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Author SHA1 Message Date
Maxim Mikityanskiy
2fa7d94afc bpf: Fix the off-by-two error in range markings 
The first commit cited below attempts to fix the off-by-one error that
appeared in some comparisons with an open range. Due to this error,
arithmetically equivalent pieces of code could get different verdicts
from the verifier, for example (pseudocode):

  // 1. Passes the verifier:
  if (data + 8 > data_end)
      return early
  read *(u64 *)data, i.e. [data; data+7]

  // 2. Rejected by the verifier (should still pass):
  if (data + 7 >= data_end)
      return early
  read *(u64 *)data, i.e. [data; data+7]

The attempted fix, however, shifts the range by one in a wrong
direction, so the bug not only remains, but also such piece of code
starts failing in the verifier:

  // 3. Rejected by the verifier, but the check is stricter than in #1.
  if (data + 8 >= data_end)
      return early
  read *(u64 *)data, i.e. [data; data+7]

The change performed by that fix converted an off-by-one bug into
off-by-two. The second commit cited below added the BPF selftests
written to ensure than code chunks like #3 are rejected, however,
they should be accepted.

This commit fixes the off-by-two error by adjusting new_range in the
right direction and fixes the tests by changing the range into the
one that should actually fail.

Fixes: fb2a311a31 ("bpf: fix off by one for range markings with L{T, E} patterns")
Fixes: b37242c773 ("bpf: add test cases to bpf selftests to cover all access tests")
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211130181607.593149-1-maximmi@nvidia.com
 2021-12-03 21:44:42 +01:00
Daniel Borkmann
353050be4c bpf: Fix toctou on read-only map's constant scalar tracking 
Commit a23740ec43 ("bpf: Track contents of read-only maps as scalars") is
checking whether maps are read-only both from BPF program side and user space
side, and then, given their content is constant, reading out their data via
map->ops->map_direct_value_addr() which is then subsequently used as known
scalar value for the register, that is, it is marked as __mark_reg_known()
with the read value at verification time. Before a23740ec43, the register
content was marked as an unknown scalar so the verifier could not make any
assumptions about the map content.

The current implementation however is prone to a TOCTOU race, meaning, the
value read as known scalar for the register is not guaranteed to be exactly
the same at a later point when the program is executed, and as such, the
prior made assumptions of the verifier with regards to the program will be
invalid which can cause issues such as OOB access, etc.

While the BPF_F_RDONLY_PROG map flag is always fixed and required to be
specified at map creation time, the map->frozen property is initially set to
false for the map given the map value needs to be populated, e.g. for global
data sections. Once complete, the loader "freezes" the map from user space
such that no subsequent updates/deletes are possible anymore. For the rest
of the lifetime of the map, this freeze one-time trigger cannot be undone
anymore after a successful BPF_MAP_FREEZE cmd return. Meaning, any new BPF_*
cmd calls which would update/delete map entries will be rejected with -EPERM
since map_get_sys_perms() removes the FMODE_CAN_WRITE permission. This also
means that pending update/delete map entries must still complete before this
guarantee is given. This corner case is not an issue for loaders since they
create and prepare such program private map in successive steps.

However, a malicious user is able to trigger this TOCTOU race in two different
ways: i) via userfaultfd, and ii) via batched updates. For i) userfaultfd is
used to expand the competition interval, so that map_update_elem() can modify
the contents of the map after map_freeze() and bpf_prog_load() were executed.
This works, because userfaultfd halts the parallel thread which triggered a
map_update_elem() at the time where we copy key/value from the user buffer and
this already passed the FMODE_CAN_WRITE capability test given at that time the
map was not "frozen". Then, the main thread performs the map_freeze() and
bpf_prog_load(), and once that had completed successfully, the other thread
is woken up to complete the pending map_update_elem() which then changes the
map content. For ii) the idea of the batched update is similar, meaning, when
there are a large number of updates to be processed, it can increase the
competition interval between the two. It is therefore possible in practice to
modify the contents of the map after executing map_freeze() and bpf_prog_load().

One way to fix both i) and ii) at the same time is to expand the use of the
map's map->writecnt. The latter was introduced in fc9702273e ("bpf: Add mmap()
support for BPF_MAP_TYPE_ARRAY") and further refined in 1f6cb19be2 ("bpf:
Prevent re-mmap()'ing BPF map as writable for initially r/o mapping") with
the rationale to make a writable mmap()'ing of a map mutually exclusive with
read-only freezing. The counter indicates writable mmap() mappings and then
prevents/fails the freeze operation. Its semantics can be expanded beyond
just mmap() by generally indicating ongoing write phases. This would essentially
span any parallel regular and batched flavor of update/delete operation and
then also have map_freeze() fail with -EBUSY. For the check_mem_access() in
the verifier we expand upon the bpf_map_is_rdonly() check ensuring that all
last pending writes have completed via bpf_map_write_active() test. Once the
map->frozen is set and bpf_map_write_active() indicates a map->writecnt of 0
only then we are really guaranteed to use the map's data as known constants.
For map->frozen being set and pending writes in process of still being completed
we fall back to marking that register as unknown scalar so we don't end up
making assumptions about it. With this, both TOCTOU reproducers from i) and
ii) are fixed.

Note that the map->writecnt has been converted into a atomic64 in the fix in
order to avoid a double freeze_mutex mutex_{un,}lock() pair when updating
map->writecnt in the various map update/delete BPF_* cmd flavors. Spanning
the freeze_mutex over entire map update/delete operations in syscall side
would not be possible due to then causing everything to be serialized.
Similarly, something like synchronize_rcu() after setting map->frozen to wait
for update/deletes to complete is not possible either since it would also
have to span the user copy which can sleep. On the libbpf side, this won't
break d66562fba1 ("libbpf: Add BPF object skeleton support") as the
anonymous mmap()-ed "map initialization image" is remapped as a BPF map-backed
mmap()-ed memory where for .rodata it's non-writable.

Fixes: a23740ec43 ("bpf: Track contents of read-only maps as scalars")
Reported-by: w1tcher.bupt@gmail.com
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
 2021-11-15 20:47:07 -08:00
Dmitrii Banshchikov
5e0bc3082e bpf: Forbid bpf_ktime_get_coarse_ns and bpf_timer_* in tracing progs 
Use of bpf_ktime_get_coarse_ns() and bpf_timer_* helpers in tracing
progs may result in locking issues.

bpf_ktime_get_coarse_ns() uses ktime_get_coarse_ns() time accessor that
isn't safe for any context:
======================================================
WARNING: possible circular locking dependency detected
5.15.0-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/14877 is trying to acquire lock:
ffffffff8cb30008 (tk_core.seq.seqcount){----}-{0:0}, at: ktime_get_coarse_ts64+0x25/0x110 kernel/time/timekeeping.c:2255

but task is already holding lock:
ffffffff90dbf200 (&obj_hash[i].lock){-.-.}-{2:2}, at: debug_object_deactivate+0x61/0x400 lib/debugobjects.c:735

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&obj_hash[i].lock){-.-.}-{2:2}:
       lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
       __debug_object_init+0xd9/0x1860 lib/debugobjects.c:569
       debug_hrtimer_init kernel/time/hrtimer.c:414 [inline]
       debug_init kernel/time/hrtimer.c:468 [inline]
       hrtimer_init+0x20/0x40 kernel/time/hrtimer.c:1592
       ntp_init_cmos_sync kernel/time/ntp.c:676 [inline]
       ntp_init+0xa1/0xad kernel/time/ntp.c:1095
       timekeeping_init+0x512/0x6bf kernel/time/timekeeping.c:1639
       start_kernel+0x267/0x56e init/main.c:1030
       secondary_startup_64_no_verify+0xb1/0xbb

-> #0 (tk_core.seq.seqcount){----}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3051 [inline]
       check_prevs_add kernel/locking/lockdep.c:3174 [inline]
       validate_chain+0x1dfb/0x8240 kernel/locking/lockdep.c:3789
       __lock_acquire+0x1382/0x2b00 kernel/locking/lockdep.c:5015
       lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625
       seqcount_lockdep_reader_access+0xfe/0x230 include/linux/seqlock.h:103
       ktime_get_coarse_ts64+0x25/0x110 kernel/time/timekeeping.c:2255
       ktime_get_coarse include/linux/timekeeping.h:120 [inline]
       ktime_get_coarse_ns include/linux/timekeeping.h:126 [inline]
       ____bpf_ktime_get_coarse_ns kernel/bpf/helpers.c:173 [inline]
       bpf_ktime_get_coarse_ns+0x7e/0x130 kernel/bpf/helpers.c:171
       bpf_prog_a99735ebafdda2f1+0x10/0xb50
       bpf_dispatcher_nop_func include/linux/bpf.h:721 [inline]
       __bpf_prog_run include/linux/filter.h:626 [inline]
       bpf_prog_run include/linux/filter.h:633 [inline]
       BPF_PROG_RUN_ARRAY include/linux/bpf.h:1294 [inline]
       trace_call_bpf+0x2cf/0x5d0 kernel/trace/bpf_trace.c:127
       perf_trace_run_bpf_submit+0x7b/0x1d0 kernel/events/core.c:9708
       perf_trace_lock+0x37c/0x440 include/trace/events/lock.h:39
       trace_lock_release+0x128/0x150 include/trace/events/lock.h:58
       lock_release+0x82/0x810 kernel/locking/lockdep.c:5636
       __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:149 [inline]
       _raw_spin_unlock_irqrestore+0x75/0x130 kernel/locking/spinlock.c:194
       debug_hrtimer_deactivate kernel/time/hrtimer.c:425 [inline]
       debug_deactivate kernel/time/hrtimer.c:481 [inline]
       __run_hrtimer kernel/time/hrtimer.c:1653 [inline]
       __hrtimer_run_queues+0x2f9/0xa60 kernel/time/hrtimer.c:1749
       hrtimer_interrupt+0x3b3/0x1040 kernel/time/hrtimer.c:1811
       local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1086 [inline]
       __sysvec_apic_timer_interrupt+0xf9/0x270 arch/x86/kernel/apic/apic.c:1103
       sysvec_apic_timer_interrupt+0x8c/0xb0 arch/x86/kernel/apic/apic.c:1097
       asm_sysvec_apic_timer_interrupt+0x12/0x20
       __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
       _raw_spin_unlock_irqrestore+0xd4/0x130 kernel/locking/spinlock.c:194
       try_to_wake_up+0x702/0xd20 kernel/sched/core.c:4118
       wake_up_process kernel/sched/core.c:4200 [inline]
       wake_up_q+0x9a/0xf0 kernel/sched/core.c:953
       futex_wake+0x50f/0x5b0 kernel/futex/waitwake.c:184
       do_futex+0x367/0x560 kernel/futex/syscalls.c:127
       __do_sys_futex kernel/futex/syscalls.c:199 [inline]
       __se_sys_futex+0x401/0x4b0 kernel/futex/syscalls.c:180
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

There is a possible deadlock with bpf_timer_* set of helpers:
hrtimer_start()
  lock_base();
  trace_hrtimer...()
    perf_event()
      bpf_run()
        bpf_timer_start()
          hrtimer_start()
            lock_base()         <- DEADLOCK

Forbid use of bpf_ktime_get_coarse_ns() and bpf_timer_* helpers in
BPF_PROG_TYPE_KPROBE, BPF_PROG_TYPE_TRACEPOINT, BPF_PROG_TYPE_PERF_EVENT
and BPF_PROG_TYPE_RAW_TRACEPOINT prog types.

Fixes: d055126180 ("bpf: Add bpf_ktime_get_coarse_ns helper")
Fixes: b00628b1c7 ("bpf: Introduce bpf timers.")
Reported-by: syzbot+43fd005b5a1b4d10781e@syzkaller.appspotmail.com
Signed-off-by: Dmitrii Banshchikov <me@ubique.spb.ru>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211113142227.566439-2-me@ubique.spb.ru
 2021-11-15 20:35:58 -08:00
Alexei Starovoitov
34d11a440c bpf: Fix inner map state pruning regression. 
Introduction of map_uid made two lookups from outer map to be distinct.
That distinction is only necessary when inner map has an embedded timer.
Otherwise it will make the verifier state pruning to be conservative
which will cause complex programs to hit 1M insn_processed limit.
Tighten map_uid logic to apply to inner maps with timers only.

Fixes: 3e8ce29850 ("bpf: Prevent pointer mismatch in bpf_timer_init.")
Reported-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Lorenz Bauer <lmb@cloudflare.com>
Link: https://lore.kernel.org/bpf/CACAyw99hVEJFoiBH_ZGyy=+oO-jyydoz6v1DeKPKs2HVsUH28w@mail.gmail.com
Link: https://lore.kernel.org/bpf/20211110172556.20754-1-alexei.starovoitov@gmail.com
 2021-11-12 16:19:40 +01:00
Martin KaFai Lau
3990ed4c42 bpf: Stop caching subprog index in the bpf_pseudo_func insn 
This patch is to fix an out-of-bound access issue when jit-ing the
bpf_pseudo_func insn (i.e. ld_imm64 with src_reg == BPF_PSEUDO_FUNC)

In jit_subprog(), it currently reuses the subprog index cached in
insn[1].imm.  This subprog index is an index into a few array related
to subprogs.  For example, in jit_subprog(), it is an index to the newly
allocated 'struct bpf_prog **func' array.

The subprog index was cached in insn[1].imm after add_subprog().  However,
this could become outdated (and too big in this case) if some subprogs
are completely removed during dead code elimination (in
adjust_subprog_starts_after_remove).  The cached index in insn[1].imm
is not updated accordingly and causing out-of-bound issue in the later
jit_subprog().

Unlike bpf_pseudo_'func' insn, the current bpf_pseudo_'call' insn
is handling the DCE properly by calling find_subprog(insn->imm) to
figure out the index instead of caching the subprog index.
The existing bpf_adj_branches() will adjust the insn->imm
whenever insn is added or removed.

Instead of having two ways handling subprog index,
this patch is to make bpf_pseudo_func works more like
bpf_pseudo_call.

First change is to stop caching the subprog index result
in insn[1].imm after add_subprog().  The verification
process will use find_subprog(insn->imm) to figure
out the subprog index.

Second change is in bpf_adj_branches() and have it to
adjust the insn->imm for the bpf_pseudo_func insn also
whenever insn is added or removed.

Third change is in jit_subprog().  Like the bpf_pseudo_call handling,
bpf_pseudo_func temporarily stores the find_subprog() result
in insn->off.  It is fine because the prog's insn has been finalized
at this point.  insn->off will be reset back to 0 later to avoid
confusing the userspace prog dump tool.

Fixes: 69c087ba62 ("bpf: Add bpf_for_each_map_elem() helper")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211106014014.651018-1-kafai@fb.com
 2021-11-06 12:54:12 -07:00
Martin KaFai Lau
f30d4968e9 bpf: Do not reject when the stack read size is different from the tracked scalar size 
Below is a simplified case from a report in bcc [0]:

  r4 = 20
  *(u32 *)(r10 -4) = r4
  *(u32 *)(r10 -8) = r4  /* r4 state is tracked */
  r4 = *(u64 *)(r10 -8)  /* Read more than the tracked 32bit scalar.
			  * verifier rejects as 'corrupted spill memory'.
			  */

After commit 354e8f1970 ("bpf: Support <8-byte scalar spill and refill"),
the 8-byte aligned 32bit spill is also tracked by the verifier and the
register state is stored.

However, if 8 bytes are read from the stack instead of the tracked 4 byte
scalar, then verifier currently rejects the program as "corrupted spill
memory". This patch fixes this case by allowing it to read but marks the
register as unknown.

Also note that, if the prog is trying to corrupt/leak an earlier spilled
pointer by spilling another <8 bytes register on top, this has already
been rejected in the check_stack_write_fixed_off().

  [0] https://github.com/iovisor/bcc/pull/3683

Fixes: 354e8f1970 ("bpf: Support <8-byte scalar spill and refill")
Reported-by: Hengqi Chen <hengqi.chen@gmail.com>
Reported-by: Yonghong Song <yhs@gmail.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Hengqi Chen <hengqi.chen@gmail.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211102064535.316018-1-kafai@fb.com
 2021-11-03 15:46:46 +01:00
Linus Torvalds
fc02cb2b37 Core: 
- Remove socket skb caches
 
  - Add a SO_RESERVE_MEM socket op to forward allocate buffer space
    and avoid memory accounting overhead on each message sent
 
  - Introduce managed neighbor entries - added by control plane and
    resolved by the kernel for use in acceleration paths (BPF / XDP
    right now, HW offload users will benefit as well)
 
  - Make neighbor eviction on link down controllable by userspace
    to work around WiFi networks with bad roaming implementations
 
  - vrf: Rework interaction with netfilter/conntrack
 
  - fq_codel: implement L4S style ce_threshold_ect1 marking
 
  - sch: Eliminate unnecessary RCU waits in mini_qdisc_pair_swap()
 
 BPF:
 
  - Add support for new btf kind BTF_KIND_TAG, arbitrary type tagging
    as implemented in LLVM14
 
  - Introduce bpf_get_branch_snapshot() to capture Last Branch Records
 
  - Implement variadic trace_printk helper
 
  - Add a new Bloomfilter map type
 
  - Track <8-byte scalar spill and refill
 
  - Access hw timestamp through BPF's __sk_buff
 
  - Disallow unprivileged BPF by default
 
  - Document BPF licensing
 
 Netfilter:
 
  - Introduce egress hook for looking at raw outgoing packets
 
  - Allow matching on and modifying inner headers / payload data
 
  - Add NFT_META_IFTYPE to match on the interface type either from
    ingress or egress
 
 Protocols:
 
  - Multi-Path TCP:
    - increase default max additional subflows to 2
    - rework forward memory allocation
    - add getsockopts: MPTCP_INFO, MPTCP_TCPINFO, MPTCP_SUBFLOW_ADDRS
 
  - MCTP flow support allowing lower layer drivers to configure msg
    muxing as needed
 
  - Automatic Multicast Tunneling (AMT) driver based on RFC7450
 
  - HSR support the redbox supervision frames (IEC-62439-3:2018)
 
  - Support for the ip6ip6 encapsulation of IOAM
 
  - Netlink interface for CAN-FD's Transmitter Delay Compensation
 
  - Support SMC-Rv2 eliminating the current same-subnet restriction,
    by exploiting the UDP encapsulation feature of RoCE adapters
 
  - TLS: add SM4 GCM/CCM crypto support
 
  - Bluetooth: initial support for link quality and audio/codec
    offload
 
 Driver APIs:
 
  - Add a batched interface for RX buffer allocation in AF_XDP
    buffer pool
 
  - ethtool: Add ability to control transceiver modules' power mode
 
  - phy: Introduce supported interfaces bitmap to express MAC
    capabilities and simplify PHY code
 
  - Drop rtnl_lock from DSA .port_fdb_{add,del} callbacks
 
 New drivers:
 
  - WiFi driver for Realtek 8852AE 802.11ax devices (rtw89)
 
  - Ethernet driver for ASIX AX88796C SPI device (x88796c)
 
 Drivers:
 
  - Broadcom PHYs
    - support 72165, 7712 16nm PHYs
    - support IDDQ-SR for additional power savings
 
  - PHY support for QCA8081, QCA9561 PHYs
 
  - NXP DPAA2: support for IRQ coalescing
 
  - NXP Ethernet (enetc): support for software TCP segmentation
 
  - Renesas Ethernet (ravb) - support DMAC and EMAC blocks of
    Gigabit-capable IP found on RZ/G2L SoC
 
  - Intel 100G Ethernet
    - support for eswitch offload of TC/OvS flow API, including
      offload of GRE, VxLAN, Geneve tunneling
    - support application device queues - ability to assign Rx and Tx
      queues to application threads
    - PTP and PPS (pulse-per-second) extensions
 
  - Broadcom Ethernet (bnxt)
    - devlink health reporting and device reload extensions
 
  - Mellanox Ethernet (mlx5)
    - offload macvlan interfaces
    - support HW offload of TC rules involving OVS internal ports
    - support HW-GRO and header/data split
    - support application device queues
 
  - Marvell OcteonTx2:
    - add XDP support for PF
    - add PTP support for VF
 
  - Qualcomm Ethernet switch (qca8k): support for QCA8328
 
  - Realtek Ethernet DSA switch (rtl8366rb)
    - support bridge offload
    - support STP, fast aging, disabling address learning
    - support for Realtek RTL8365MB-VC, a 4+1 port 10M/100M/1GE switch
 
  - Mellanox Ethernet/IB switch (mlxsw)
    - multi-level qdisc hierarchy offload (e.g. RED, prio and shaping)
    - offload root TBF qdisc as port shaper
    - support multiple routing interface MAC address prefixes
    - support for IP-in-IP with IPv6 underlay
 
  - MediaTek WiFi (mt76)
    - mt7921 - ASPM, 6GHz, SDIO and testmode support
    - mt7915 - LED and TWT support
 
  - Qualcomm WiFi (ath11k)
    - include channel rx and tx time in survey dump statistics
    - support for 80P80 and 160 MHz bandwidths
    - support channel 2 in 6 GHz band
    - spectral scan support for QCN9074
    - support for rx decapsulation offload (data frames in 802.3
      format)
 
  - Qualcomm phone SoC WiFi (wcn36xx)
    - enable Idle Mode Power Save (IMPS) to reduce power consumption
      during idle
 
  - Bluetooth driver support for MediaTek MT7922 and MT7921
 
  - Enable support for AOSP Bluetooth extension in Qualcomm WCN399x
    and Realtek 8822C/8852A
 
  - Microsoft vNIC driver (mana)
    - support hibernation and kexec
 
  - Google vNIC driver (gve)
    - support for jumbo frames
    - implement Rx page reuse
 
 Refactor:
 
  - Make all writes to netdev->dev_addr go thru helpers, so that we
    can add this address to the address rbtree and handle the updates
 
  - Various TCP cleanups and optimizations including improvements
    to CPU cache use
 
  - Simplify the gnet_stats, Qdisc stats' handling and remove
    qdisc->running sequence counter
 
  - Driver changes and API updates to address devlink locking
    deficiencies
 
 Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Merge tag 'net-next-for-5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next

Pull networking updates from Jakub Kicinski:
 "Core:

   - Remove socket skb caches

   - Add a SO_RESERVE_MEM socket op to forward allocate buffer space and
     avoid memory accounting overhead on each message sent

   - Introduce managed neighbor entries - added by control plane and
     resolved by the kernel for use in acceleration paths (BPF / XDP
     right now, HW offload users will benefit as well)

   - Make neighbor eviction on link down controllable by userspace to
     work around WiFi networks with bad roaming implementations

   - vrf: Rework interaction with netfilter/conntrack

   - fq_codel: implement L4S style ce_threshold_ect1 marking

   - sch: Eliminate unnecessary RCU waits in mini_qdisc_pair_swap()

  BPF:

   - Add support for new btf kind BTF_KIND_TAG, arbitrary type tagging
     as implemented in LLVM14

   - Introduce bpf_get_branch_snapshot() to capture Last Branch Records

   - Implement variadic trace_printk helper

   - Add a new Bloomfilter map type

   - Track <8-byte scalar spill and refill

   - Access hw timestamp through BPF's __sk_buff

   - Disallow unprivileged BPF by default

   - Document BPF licensing

  Netfilter:

   - Introduce egress hook for looking at raw outgoing packets

   - Allow matching on and modifying inner headers / payload data

   - Add NFT_META_IFTYPE to match on the interface type either from
     ingress or egress

  Protocols:

   - Multi-Path TCP:
      - increase default max additional subflows to 2
      - rework forward memory allocation
      - add getsockopts: MPTCP_INFO, MPTCP_TCPINFO, MPTCP_SUBFLOW_ADDRS

   - MCTP flow support allowing lower layer drivers to configure msg
     muxing as needed

   - Automatic Multicast Tunneling (AMT) driver based on RFC7450

   - HSR support the redbox supervision frames (IEC-62439-3:2018)

   - Support for the ip6ip6 encapsulation of IOAM

   - Netlink interface for CAN-FD's Transmitter Delay Compensation

   - Support SMC-Rv2 eliminating the current same-subnet restriction, by
     exploiting the UDP encapsulation feature of RoCE adapters

   - TLS: add SM4 GCM/CCM crypto support

   - Bluetooth: initial support for link quality and audio/codec offload

  Driver APIs:

   - Add a batched interface for RX buffer allocation in AF_XDP buffer
     pool

   - ethtool: Add ability to control transceiver modules' power mode

   - phy: Introduce supported interfaces bitmap to express MAC
     capabilities and simplify PHY code

   - Drop rtnl_lock from DSA .port_fdb_{add,del} callbacks

  New drivers:

   - WiFi driver for Realtek 8852AE 802.11ax devices (rtw89)

   - Ethernet driver for ASIX AX88796C SPI device (x88796c)

  Drivers:

   - Broadcom PHYs
      - support 72165, 7712 16nm PHYs
      - support IDDQ-SR for additional power savings

   - PHY support for QCA8081, QCA9561 PHYs

   - NXP DPAA2: support for IRQ coalescing

   - NXP Ethernet (enetc): support for software TCP segmentation

   - Renesas Ethernet (ravb) - support DMAC and EMAC blocks of
     Gigabit-capable IP found on RZ/G2L SoC

   - Intel 100G Ethernet
      - support for eswitch offload of TC/OvS flow API, including
        offload of GRE, VxLAN, Geneve tunneling
      - support application device queues - ability to assign Rx and Tx
        queues to application threads
      - PTP and PPS (pulse-per-second) extensions

   - Broadcom Ethernet (bnxt)
      - devlink health reporting and device reload extensions

   - Mellanox Ethernet (mlx5)
      - offload macvlan interfaces
      - support HW offload of TC rules involving OVS internal ports
      - support HW-GRO and header/data split
      - support application device queues

   - Marvell OcteonTx2:
      - add XDP support for PF
      - add PTP support for VF

   - Qualcomm Ethernet switch (qca8k): support for QCA8328

   - Realtek Ethernet DSA switch (rtl8366rb)
      - support bridge offload
      - support STP, fast aging, disabling address learning
      - support for Realtek RTL8365MB-VC, a 4+1 port 10M/100M/1GE switch

   - Mellanox Ethernet/IB switch (mlxsw)
      - multi-level qdisc hierarchy offload (e.g. RED, prio and shaping)
      - offload root TBF qdisc as port shaper
      - support multiple routing interface MAC address prefixes
      - support for IP-in-IP with IPv6 underlay

   - MediaTek WiFi (mt76)
      - mt7921 - ASPM, 6GHz, SDIO and testmode support
      - mt7915 - LED and TWT support

   - Qualcomm WiFi (ath11k)
      - include channel rx and tx time in survey dump statistics
      - support for 80P80 and 160 MHz bandwidths
      - support channel 2 in 6 GHz band
      - spectral scan support for QCN9074
      - support for rx decapsulation offload (data frames in 802.3
        format)

   - Qualcomm phone SoC WiFi (wcn36xx)
      - enable Idle Mode Power Save (IMPS) to reduce power consumption
        during idle

   - Bluetooth driver support for MediaTek MT7922 and MT7921

   - Enable support for AOSP Bluetooth extension in Qualcomm WCN399x and
     Realtek 8822C/8852A

   - Microsoft vNIC driver (mana)
      - support hibernation and kexec

   - Google vNIC driver (gve)
      - support for jumbo frames
      - implement Rx page reuse

  Refactor:

   - Make all writes to netdev->dev_addr go thru helpers, so that we can
     add this address to the address rbtree and handle the updates

   - Various TCP cleanups and optimizations including improvements to
     CPU cache use

   - Simplify the gnet_stats, Qdisc stats' handling and remove
     qdisc->running sequence counter

   - Driver changes and API updates to address devlink locking
     deficiencies"

* tag 'net-next-for-5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (2122 commits)
  Revert "net: avoid double accounting for pure zerocopy skbs"
  selftests: net: add arp_ndisc_evict_nocarrier
  net: ndisc: introduce ndisc_evict_nocarrier sysctl parameter
  net: arp: introduce arp_evict_nocarrier sysctl parameter
  libbpf: Deprecate AF_XDP support
  kbuild: Unify options for BTF generation for vmlinux and modules
  selftests/bpf: Add a testcase for 64-bit bounds propagation issue.
  bpf: Fix propagation of signed bounds from 64-bit min/max into 32-bit.
  bpf: Fix propagation of bounds from 64-bit min/max into 32-bit and var_off.
  net: vmxnet3: remove multiple false checks in vmxnet3_ethtool.c
  net: avoid double accounting for pure zerocopy skbs
  tcp: rename sk_wmem_free_skb
  netdevsim: fix uninit value in nsim_drv_configure_vfs()
  selftests/bpf: Fix also no-alu32 strobemeta selftest
  bpf: Add missing map_delete_elem method to bloom filter map
  selftests/bpf: Add bloom map success test for userspace calls
  bpf: Add alignment padding for "map_extra" + consolidate holes
  bpf: Bloom filter map naming fixups
  selftests/bpf: Add test cases for struct_ops prog
  bpf: Add dummy BPF STRUCT_OPS for test purpose
  ...
 2021-11-02 06:20:58 -07:00
Alexei Starovoitov
388e2c0b97 bpf: Fix propagation of signed bounds from 64-bit min/max into 32-bit. 
Similar to unsigned bounds propagation fix signed bounds.
The 'Fixes' tag is a hint. There is no security bug here.
The verifier was too conservative.

Fixes: 3f50f132d8 ("bpf: Verifier, do explicit ALU32 bounds tracking")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211101222153.78759-2-alexei.starovoitov@gmail.com
 2021-11-01 18:05:12 -07:00
Alexei Starovoitov
b9979db834 bpf: Fix propagation of bounds from 64-bit min/max into 32-bit and var_off. 
Before this fix:
166: (b5) if r2 <= 0x1 goto pc+22
from 166 to 189: R2=invP(id=1,umax_value=1,var_off=(0x0; 0xffffffff))

After this fix:
166: (b5) if r2 <= 0x1 goto pc+22
from 166 to 189: R2=invP(id=1,umax_value=1,var_off=(0x0; 0x1))

While processing BPF_JLE the reg_set_min_max() would set true_reg->umax_value = 1
and call __reg_combine_64_into_32(true_reg).

Without the fix it would not pass the condition:
if (__reg64_bound_u32(reg->umin_value) && __reg64_bound_u32(reg->umax_value))

since umin_value == 0 at this point.
Before commit 10bf4e8316 the umin was incorrectly ingored.
The commit 10bf4e8316 fixed the correctness issue, but pessimized
propagation of 64-bit min max into 32-bit min max and corresponding var_off.

Fixes: 10bf4e8316 ("bpf: Fix propagation of 32 bit unsigned bounds from 64 bit bounds")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211101222153.78759-1-alexei.starovoitov@gmail.com
 2021-11-01 18:05:11 -07:00
Joanne Koong
9330986c03 bpf: Add bloom filter map implementation 
This patch adds the kernel-side changes for the implementation of
a bpf bloom filter map.

The bloom filter map supports peek (determining whether an element
is present in the map) and push (adding an element to the map)
operations.These operations are exposed to userspace applications
through the already existing syscalls in the following way:

BPF_MAP_LOOKUP_ELEM -> peek
BPF_MAP_UPDATE_ELEM -> push

The bloom filter map does not have keys, only values. In light of
this, the bloom filter map's API matches that of queue stack maps:
user applications use BPF_MAP_LOOKUP_ELEM/BPF_MAP_UPDATE_ELEM
which correspond internally to bpf_map_peek_elem/bpf_map_push_elem,
and bpf programs must use the bpf_map_peek_elem and bpf_map_push_elem
APIs to query or add an element to the bloom filter map. When the
bloom filter map is created, it must be created with a key_size of 0.

For updates, the user will pass in the element to add to the map
as the value, with a NULL key. For lookups, the user will pass in the
element to query in the map as the value, with a NULL key. In the
verifier layer, this requires us to modify the argument type of
a bloom filter's BPF_FUNC_map_peek_elem call to ARG_PTR_TO_MAP_VALUE;
as well, in the syscall layer, we need to copy over the user value
so that in bpf_map_peek_elem, we know which specific value to query.

A few things to please take note of:
 * If there are any concurrent lookups + updates, the user is
responsible for synchronizing this to ensure no false negative lookups
occur.
 * The number of hashes to use for the bloom filter is configurable from
userspace. If no number is specified, the default used will be 5 hash
functions. The benchmarks later in this patchset can help compare the
performance of using different number of hashes on different entry
sizes. In general, using more hashes decreases both the false positive
rate and the speed of a lookup.
 * Deleting an element in the bloom filter map is not supported.
 * The bloom filter map may be used as an inner map.
 * The "max_entries" size that is specified at map creation time is used
to approximate a reasonable bitmap size for the bloom filter, and is not
otherwise strictly enforced. If the user wishes to insert more entries
into the bloom filter than "max_entries", they may do so but they should
be aware that this may lead to a higher false positive rate.

Signed-off-by: Joanne Koong <joannekoong@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211027234504.30744-2-joannekoong@fb.com
 2021-10-28 13:22:49 -07:00
Dave Marchevsky
aba64c7da9 bpf: Add verified_insns to bpf_prog_info and fdinfo 
This stat is currently printed in the verifier log and not stored
anywhere. To ease consumption of this data, add a field to bpf_prog_aux
so it can be exposed via BPF_OBJ_GET_INFO_BY_FD and fdinfo.

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20211020074818.1017682-2-davemarchevsky@fb.com
 2021-10-21 15:51:47 -07:00
Kumar Kartikeya Dwivedi
588cd7ef53 bpf: Silence Coverity warning for find_kfunc_desc_btf 
The helper function returns a pointer that in the failure case encodes
an error in the struct btf pointer. The current code lead to Coverity
warning about the use of the invalid pointer:

 *** CID 1507963:  Memory - illegal accesses  (USE_AFTER_FREE)
 /kernel/bpf/verifier.c: 1788 in find_kfunc_desc_btf()
 1782                          return ERR_PTR(-EINVAL);
 1783                  }
 1784
 1785                  kfunc_btf = __find_kfunc_desc_btf(env, offset, btf_modp);
 1786                  if (IS_ERR_OR_NULL(kfunc_btf)) {
 1787                          verbose(env, "cannot find module BTF for func_id %u\n", func_id);
 >>>      CID 1507963:  Memory - illegal accesses  (USE_AFTER_FREE)
 >>>      Using freed pointer "kfunc_btf".
 1788                          return kfunc_btf ?: ERR_PTR(-ENOENT);
 1789                  }
 1790                  return kfunc_btf;
 1791          }
 1792          return btf_vmlinux ?: ERR_PTR(-ENOENT);
 1793     }

Daniel suggested the use of ERR_CAST so that the intended use is clear
to Coverity, but on closer look it seems that we never return NULL from
the helper. Andrii noted that since __find_kfunc_desc_btf already logs
errors for all cases except btf_get_by_fd, it is much easier to add
logging for that and remove the IS_ERR check altogether, returning
directly from it.

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211009040900.803436-1-memxor@gmail.com
 2021-10-19 16:55:50 -07:00
Matthew Wilcox (Oracle)
9dd3d06940 mm/filemap: Add filemap_add_folio() 
Convert __add_to_page_cache_locked() into __filemap_add_folio().
Add an assertion to it that (for !hugetlbfs), the folio is naturally
aligned within the file.  Move the prototype from mm.h to pagemap.h.
Convert add_to_page_cache_lru() into filemap_add_folio().  Add a
compatibility wrapper for unconverted callers.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
 2021-10-18 07:49:40 -04:00
Andrey Ignatov
0640c77c46 bpf: Avoid retpoline for bpf_for_each_map_elem 
Similarly to 09772d92cd ("bpf: avoid retpoline for
lookup/update/delete calls on maps") and 84430d4232 ("bpf, verifier:
avoid retpoline for map push/pop/peek operation") avoid indirect call
while calling bpf_for_each_map_elem.

Before (a program fragment):

  ; if (rules_map) {
   142: (15) if r4 == 0x0 goto pc+8
   143: (bf) r3 = r10
  ; bpf_for_each_map_elem(rules_map, process_each_rule, &ctx, 0);
   144: (07) r3 += -24
   145: (bf) r1 = r4
   146: (18) r2 = subprog[+5]
   148: (b7) r4 = 0
   149: (85) call bpf_for_each_map_elem#143680  <-- indirect call via
                                                    helper

After (same program fragment):

   ; if (rules_map) {
    142: (15) if r4 == 0x0 goto pc+8
    143: (bf) r3 = r10
   ; bpf_for_each_map_elem(rules_map, process_each_rule, &ctx, 0);
    144: (07) r3 += -24
    145: (bf) r1 = r4
    146: (18) r2 = subprog[+5]
    148: (b7) r4 = 0
    149: (85) call bpf_for_each_array_elem#170336  <-- direct call

On a benchmark that calls bpf_for_each_map_elem() once and does many
other things (mostly checking fields in skb) with CONFIG_RETPOLINE=y it
makes program faster.

Before:

  ============================================================================
  Benchmark.cpp                                              time/iter iters/s
  ============================================================================
  IngressMatchByRemoteEndpoint                                80.78ns 12.38M
  IngressMatchByRemoteIP                                      80.66ns 12.40M
  IngressMatchByRemotePort                                    80.87ns 12.37M

After:

  ============================================================================
  Benchmark.cpp                                              time/iter iters/s
  ============================================================================
  IngressMatchByRemoteEndpoint                                73.49ns 13.61M
  IngressMatchByRemoteIP                                      71.48ns 13.99M
  IngressMatchByRemotePort                                    70.39ns 14.21M

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211006001838.75607-1-rdna@fb.com
 2021-10-05 19:22:33 -07:00
Kumar Kartikeya Dwivedi
a5d8272752 bpf: Be conservative while processing invalid kfunc calls 
This patch also modifies the BPF verifier to only return error for
invalid kfunc calls specially marked by userspace (with insn->imm == 0,
insn->off == 0) after the verifier has eliminated dead instructions.
This can be handled in the fixup stage, and skip processing during add
and check stages.

If such an invalid call is dropped, the fixup stage will not encounter
insn->imm as 0, otherwise it bails out and returns an error.

This will be exposed as weak ksym support in libbpf in later patches.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211002011757.311265-3-memxor@gmail.com
 2021-10-05 17:07:41 -07:00
Kumar Kartikeya Dwivedi
2357672c54 bpf: Introduce BPF support for kernel module function calls 
This change adds support on the kernel side to allow for BPF programs to
call kernel module functions. Userspace will prepare an array of module
BTF fds that is passed in during BPF_PROG_LOAD using fd_array parameter.
In the kernel, the module BTFs are placed in the auxilliary struct for
bpf_prog, and loaded as needed.

The verifier then uses insn->off to index into the fd_array. insn->off
0 is reserved for vmlinux BTF (for backwards compat), so userspace must
use an fd_array index > 0 for module kfunc support. kfunc_btf_tab is
sorted based on offset in an array, and each offset corresponds to one
descriptor, with a max limit up to 256 such module BTFs.

We also change existing kfunc_tab to distinguish each element based on
imm, off pair as each such call will now be distinct.

Another change is to check_kfunc_call callback, which now include a
struct module * pointer, this is to be used in later patch such that the
kfunc_id and module pointer are matched for dynamically registered BTF
sets from loadable modules, so that same kfunc_id in two modules doesn't
lead to check_kfunc_call succeeding. For the duration of the
check_kfunc_call, the reference to struct module exists, as it returns
the pointer stored in kfunc_btf_tab.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211002011757.311265-2-memxor@gmail.com
 2021-10-05 17:07:41 -07:00
Kees Cook
3d717fad50 bpf: Replace "want address" users of BPF_CAST_CALL with BPF_CALL_IMM 
In order to keep ahead of cases in the kernel where Control Flow
Integrity (CFI) may trip over function call casts, enabling
-Wcast-function-type is helpful. To that end, BPF_CAST_CALL causes
various warnings and is one of the last places in the kernel triggering
this warning.

Most places using BPF_CAST_CALL actually just want a void * to perform
math on. It's not actually performing a call, so just use a different
helper to get the void *, by way of the new BPF_CALL_IMM() helper, which
can clean up a common copy/paste idiom as well.

This change results in no object code difference.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://github.com/KSPP/linux/issues/20
Link: https://lore.kernel.org/lkml/CAEf4Bzb46=-J5Fxc3mMZ8JQPtK1uoE0q6+g6WPz53Cvx=CBEhw@mail.gmail.com
Link: https://lore.kernel.org/bpf/20210928230946.4062144-2-keescook@chromium.org
 2021-09-28 16:27:18 -07:00
Martin KaFai Lau
354e8f1970 bpf: Support <8-byte scalar spill and refill 
The verifier currently does not save the reg state when
spilling <8byte bounded scalar to the stack.  The bpf program
will be incorrectly rejected when this scalar is refilled to
the reg and then used to offset into a packet header.
The later patch has a simplified bpf prog from a real use case
to demonstrate this case.  The current work around is
to reparse the packet again such that this offset scalar
is close to where the packet data will be accessed to
avoid the spill.  Thus, the header is parsed twice.

The llvm patch [1] will align the <8bytes spill to
the 8-byte stack address.  This can simplify the verifier
support by avoiding to store multiple reg states for
each 8 byte stack slot.

This patch changes the verifier to save the reg state when
spilling <8bytes scalar to the stack.  This reg state saving
is limited to spill aligned to the 8-byte stack address.
The current refill logic has already called coerce_reg_to_size(),
so coerce_reg_to_size() is not called on state->stack[spi].spilled_ptr
during spill.

When refilling in check_stack_read_fixed_off(),  it checks
the refill size is the same as the number of bytes marked with
STACK_SPILL before restoring the reg state.  When restoring
the reg state to state->regs[dst_regno], it needs
to avoid the state->regs[dst_regno].subreg_def being
over written because it has been marked by the check_reg_arg()
earlier [check_mem_access() is called after check_reg_arg() in
do_check()].  Reordering check_mem_access() and check_reg_arg()
will need a lot of changes in test_verifier's tests because
of the difference in verifier's error message.  Thus, the
patch here is to save the state->regs[dst_regno].subreg_def
first in check_stack_read_fixed_off().

There are cases that the verifier needs to scrub the spilled slot
from STACK_SPILL to STACK_MISC.  After this patch the spill is not always
in 8 bytes now, so it can no longer assume the other 7 bytes are always
marked as STACK_SPILL.  In particular, the scrub needs to avoid marking
an uninitialized byte from STACK_INVALID to STACK_MISC.  Otherwise, the
verifier will incorrectly accept bpf program reading uninitialized bytes
from the stack.  A new helper scrub_spilled_slot() is created for this
purpose.

[1]: https://reviews.llvm.org/D109073

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210922004941.625398-1-kafai@fb.com
 2021-09-26 13:07:27 -07:00
Martin KaFai Lau
27113c59b6 bpf: Check the other end of slot_type for STACK_SPILL 
Every 8 bytes of the stack is tracked by a bpf_stack_state.
Within each bpf_stack_state, there is a 'u8 slot_type[8]' to track
the type of each byte.  Verifier tests slot_type[0] == STACK_SPILL
to decide if the spilled reg state is saved.  Verifier currently only
saves the reg state if the whole 8 bytes are spilled to the stack,
so checking the slot_type[7] is the same as checking slot_type[0].

The later patch will allow verifier to save the bounded scalar
reg also for <8 bytes spill.  There is a llvm patch [1] to ensure
the <8 bytes spill will be 8-byte aligned,  so checking
slot_type[7] instead of slot_type[0] is required.

While at it, this patch refactors the slot_type[0] == STACK_SPILL
test into a new function is_spilled_reg() and change the
slot_type[0] check to slot_type[7] check in there also.

[1] https://reviews.llvm.org/D109073

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210922004934.624194-1-kafai@fb.com
 2021-09-26 13:07:27 -07:00
Bixuan Cui
0e6491b559 bpf: Add oversize check before call kvcalloc() 
Commit 7661809d49 ("mm: don't allow oversized kvmalloc() calls") add the
oversize check. When the allocation is larger than what kmalloc() supports,
the following warning triggered:

WARNING: CPU: 0 PID: 8408 at mm/util.c:597 kvmalloc_node+0x108/0x110 mm/util.c:597
Modules linked in:
CPU: 0 PID: 8408 Comm: syz-executor221 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:kvmalloc_node+0x108/0x110 mm/util.c:597
Call Trace:
 kvmalloc include/linux/mm.h:806 [inline]
 kvmalloc_array include/linux/mm.h:824 [inline]
 kvcalloc include/linux/mm.h:829 [inline]
 check_btf_line kernel/bpf/verifier.c:9925 [inline]
 check_btf_info kernel/bpf/verifier.c:10049 [inline]
 bpf_check+0xd634/0x150d0 kernel/bpf/verifier.c:13759
 bpf_prog_load kernel/bpf/syscall.c:2301 [inline]
 __sys_bpf+0x11181/0x126e0 kernel/bpf/syscall.c:4587
 __do_sys_bpf kernel/bpf/syscall.c:4691 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:4689 [inline]
 __x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4689
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported-by: syzbot+f3e749d4c662818ae439@syzkaller.appspotmail.com
Signed-off-by: Bixuan Cui <cuibixuan@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210911005557.45518-1-cuibixuan@huawei.com
 2021-09-13 16:28:15 -07:00
Jakub Kicinski
19a31d7921 Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 
Daniel Borkmann says:

====================
bpf-next 2021-08-31

We've added 116 non-merge commits during the last 17 day(s) which contain
a total of 126 files changed, 6813 insertions(+), 4027 deletions(-).

The main changes are:

1) Add opaque bpf_cookie to perf link which the program can read out again,
   to be used in libbpf-based USDT library, from Andrii Nakryiko.

2) Add bpf_task_pt_regs() helper to access userspace pt_regs, from Daniel Xu.

3) Add support for UNIX stream type sockets for BPF sockmap, from Jiang Wang.

4) Allow BPF TCP congestion control progs to call bpf_setsockopt() e.g. to switch
   to another congestion control algorithm during init, from Martin KaFai Lau.

5) Extend BPF iterator support for UNIX domain sockets, from Kuniyuki Iwashima.

6) Allow bpf_{set,get}sockopt() calls from setsockopt progs, from Prankur Gupta.

7) Add bpf_get_netns_cookie() helper for BPF_PROG_TYPE_{SOCK_OPS,CGROUP_SOCKOPT}
   progs, from Xu Liu and Stanislav Fomichev.

8) Support for __weak typed ksyms in libbpf, from Hao Luo.

9) Shrink struct cgroup_bpf by 504 bytes through refactoring, from Dave Marchevsky.

10) Fix a smatch complaint in verifier's narrow load handling, from Andrey Ignatov.

11) Fix BPF interpreter's tail call count limit, from Daniel Borkmann.

12) Big batch of improvements to BPF selftests, from Magnus Karlsson, Li Zhijian,
    Yucong Sun, Yonghong Song, Ilya Leoshkevich, Jussi Maki, Ilya Leoshkevich, others.

13) Another big batch to revamp XDP samples in order to give them consistent look
    and feel, from Kumar Kartikeya Dwivedi.

* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (116 commits)
  MAINTAINERS: Remove self from powerpc BPF JIT
  selftests/bpf: Fix potential unreleased lock
  samples: bpf: Fix uninitialized variable in xdp_redirect_cpu
  selftests/bpf: Reduce more flakyness in sockmap_listen
  bpf: Fix bpf-next builds without CONFIG_BPF_EVENTS
  bpf: selftests: Add dctcp fallback test
  bpf: selftests: Add connect_to_fd_opts to network_helpers
  bpf: selftests: Add sk_state to bpf_tcp_helpers.h
  bpf: tcp: Allow bpf-tcp-cc to call bpf_(get|set)sockopt
  selftests: xsk: Preface options with opt
  selftests: xsk: Make enums lower case
  selftests: xsk: Generate packets from specification
  selftests: xsk: Generate packet directly in umem
  selftests: xsk: Simplify cleanup of ifobjects
  selftests: xsk: Decrease sending speed
  selftests: xsk: Validate tx stats on tx thread
  selftests: xsk: Simplify packet validation in xsk tests
  selftests: xsk: Rename worker_* functions that are not thread entry points
  selftests: xsk: Disassociate umem size with packets sent
  selftests: xsk: Remove end-of-test packet
  ...
====================

Link: https://lore.kernel.org/r/20210830225618.11634-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
 2021-08-30 16:42:47 -07:00
Jakub Kicinski
97c78d0af5 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 
drivers/net/wwan/mhi_wwan_mbim.c - drop the extra arg.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
 2021-08-26 17:57:57 -07:00
Andrey Ignatov
d7af7e497f bpf: Fix possible out of bound write in narrow load handling 
Fix a verifier bug found by smatch static checker in [0].

This problem has never been seen in prod to my best knowledge. Fixing it
still seems to be a good idea since it's hard to say for sure whether
it's possible or not to have a scenario where a combination of
convert_ctx_access() and a narrow load would lead to an out of bound
write.

When narrow load is handled, one or two new instructions are added to
insn_buf array, but before it was only checked that

	cnt >= ARRAY_SIZE(insn_buf)

And it's safe to add a new instruction to insn_buf[cnt++] only once. The
second try will lead to out of bound write. And this is what can happen
if `shift` is set.

Fix it by making sure that if the BPF_RSH instruction has to be added in
addition to BPF_AND then there is enough space for two more instructions
in insn_buf.

The full report [0] is below:

kernel/bpf/verifier.c:12304 convert_ctx_accesses() warn: offset 'cnt' incremented past end of array
kernel/bpf/verifier.c:12311 convert_ctx_accesses() warn: offset 'cnt' incremented past end of array

kernel/bpf/verifier.c
    12282
    12283 			insn->off = off & ~(size_default - 1);
    12284 			insn->code = BPF_LDX | BPF_MEM | size_code;
    12285 		}
    12286
    12287 		target_size = 0;
    12288 		cnt = convert_ctx_access(type, insn, insn_buf, env->prog,
    12289 					 &target_size);
    12290 		if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf) ||
                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^
Bounds check.

    12291 		    (ctx_field_size && !target_size)) {
    12292 			verbose(env, "bpf verifier is misconfigured\n");
    12293 			return -EINVAL;
    12294 		}
    12295
    12296 		if (is_narrower_load && size < target_size) {
    12297 			u8 shift = bpf_ctx_narrow_access_offset(
    12298 				off, size, size_default) * 8;
    12299 			if (ctx_field_size <= 4) {
    12300 				if (shift)
    12301 					insn_buf[cnt++] = BPF_ALU32_IMM(BPF_RSH,
                                                         ^^^^^
increment beyond end of array

    12302 									insn->dst_reg,
    12303 									shift);
--> 12304 				insn_buf[cnt++] = BPF_ALU32_IMM(BPF_AND, insn->dst_reg,
                                                 ^^^^^
out of bounds write

    12305 								(1 << size * 8) - 1);
    12306 			} else {
    12307 				if (shift)
    12308 					insn_buf[cnt++] = BPF_ALU64_IMM(BPF_RSH,
    12309 									insn->dst_reg,
    12310 									shift);
    12311 				insn_buf[cnt++] = BPF_ALU64_IMM(BPF_AND, insn->dst_reg,
                                        ^^^^^^^^^^^^^^^
Same.

    12312 								(1ULL << size * 8) - 1);
    12313 			}
    12314 		}
    12315
    12316 		new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
    12317 		if (!new_prog)
    12318 			return -ENOMEM;
    12319
    12320 		delta += cnt - 1;
    12321
    12322 		/* keep walking new program and skip insns we just inserted */
    12323 		env->prog = new_prog;
    12324 		insn      = new_prog->insnsi + i + delta;
    12325 	}
    12326
    12327 	return 0;
    12328 }

[0] https://lore.kernel.org/bpf/20210817050843.GA21456@kili/

v1->v2:
- clarify that problem was only seen by static checker but not in prod;

Fixes: 46f53a65d2 ("bpf: Allow narrow loads with offset > 0")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210820163935.1902398-1-rdna@fb.com
 2021-08-24 14:32:26 -07:00
Daniel Borkmann
5b029a32cf bpf: Fix ringbuf helper function compatibility 
Commit 457f44363a ("bpf: Implement BPF ring buffer and verifier support
for it") extended check_map_func_compatibility() by enforcing map -> helper
function match, but not helper -> map type match.

Due to this all of the bpf_ringbuf_*() helper functions could be used with
a wrong map type such as array or hash map, leading to invalid access due
to type confusion.

Also, both BPF_FUNC_ringbuf_{submit,discard} have ARG_PTR_TO_ALLOC_MEM as
argument and not a BPF map. Therefore, their check_map_func_compatibility()
presence is incorrect since it's only for map type checking.

Fixes: 457f44363a ("bpf: Implement BPF ring buffer and verifier support for it")
Reported-by: Ryota Shiga (Flatt Security)
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
 2021-08-23 23:09:10 +02:00
Jakub Kicinski
f444fea789 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 
drivers/ptp/Kconfig:
  55c8fca1da ("ptp_pch: Restore dependency on PCI")
  e5f3155267 ("ethernet: fix PTP_1588_CLOCK dependencies")

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
 2021-08-19 18:09:18 -07:00
Andrii Nakryiko
fb7dd8bca0 bpf: Refactor BPF_PROG_RUN into a function 
Turn BPF_PROG_RUN into a proper always inlined function. No functional and
performance changes are intended, but it makes it much easier to understand
what's going on with how BPF programs are actually get executed. It's more
obvious what types and callbacks are expected. Also extra () around input
parameters can be dropped, as well as `__` variable prefixes intended to avoid
naming collisions, which makes the code simpler to read and write.

This refactoring also highlighted one extra issue. BPF_PROG_RUN is both
a macro and an enum value (BPF_PROG_RUN == BPF_PROG_TEST_RUN). Turning
BPF_PROG_RUN into a function causes naming conflict compilation error. So
rename BPF_PROG_RUN into lower-case bpf_prog_run(), similar to
bpf_prog_run_xdp(), bpf_prog_run_pin_on_cpu(), etc. All existing callers of
BPF_PROG_RUN, the macro, are switched to bpf_prog_run() explicitly.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210815070609.987780-2-andrii@kernel.org
 2021-08-17 00:45:07 +02:00
Ilya Leoshkevich
45c709f8c7 bpf: Clear zext_dst of dead insns 
"access skb fields ok" verifier test fails on s390 with the "verifier
bug. zext_dst is set, but no reg is defined" message. The first insns
of the test prog are ...

   0:	61 01 00 00 00 00 00 00 	ldxw %r0,[%r1+0]
   8:	35 00 00 01 00 00 00 00 	jge %r0,0,1
  10:	61 01 00 08 00 00 00 00 	ldxw %r0,[%r1+8]

... and the 3rd one is dead (this does not look intentional to me, but
this is a separate topic).

sanitize_dead_code() converts dead insns into "ja -1", but keeps
zext_dst. When opt_subreg_zext_lo32_rnd_hi32() tries to parse such
an insn, it sees this discrepancy and bails. This problem can be seen
only with JITs whose bpf_jit_needs_zext() returns true.

Fix by clearning dead insns' zext_dst.

The commits that contributed to this problem are:

1. 5aa5bd14c5 ("bpf: add initial suite for selftests"), which
   introduced the test with the dead code.
2. 5327ed3d44 ("bpf: verifier: mark verified-insn with
   sub-register zext flag"), which introduced the zext_dst flag.
3. 83a2881903 ("bpf: Account for BPF_FETCH in
   insn_has_def32()"), which introduced the sanity check.
4. 9183671af6 ("bpf: Fix leakage under speculation on
   mispredicted branches"), which bisect points to.

It's best to fix this on stable branches that contain the second one,
since that's the point where the inconsistency was introduced.

Fixes: 5327ed3d44 ("bpf: verifier: mark verified-insn with sub-register zext flag")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210812151811.184086-2-iii@linux.ibm.com
 2021-08-13 17:43:43 +02:00
Jakub Kicinski
d2e11fd2b7 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 
Conflicting commits, all resolutions pretty trivial:

drivers/bus/mhi/pci_generic.c
  5c2c853159 ("bus: mhi: pci-generic: configurable network interface MRU")
  56f6f4c4eb ("bus: mhi: pci_generic: Apply no-op for wake using sideband wake boolean")

drivers/nfc/s3fwrn5/firmware.c
  a0302ff590 ("nfc: s3fwrn5: remove unnecessary label")
  46573e3ab0 ("nfc: s3fwrn5: fix undefined parameter values in dev_err()")
  801e541c79 ("nfc: s3fwrn5: fix undefined parameter values in dev_err()")

MAINTAINERS
  7d901a1e87 ("net: phy: add Maxlinear GPY115/21x/24x driver")
  8a7b46fa79 ("MAINTAINERS: add Yasushi SHOJI as reviewer for the Microchip CAN BUS Analyzer Tool driver")

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
 2021-07-31 09:14:46 -07:00
Daniel Borkmann
2039f26f3a bpf: Fix leakage due to insufficient speculative store bypass mitigation 
Spectre v4 gadgets make use of memory disambiguation, which is a set of
techniques that execute memory access instructions, that is, loads and
stores, out of program order; Intel's optimization manual, section 2.4.4.5:

  A load instruction micro-op may depend on a preceding store. Many
  microarchitectures block loads until all preceding store addresses are
  known. The memory disambiguator predicts which loads will not depend on
  any previous stores. When the disambiguator predicts that a load does
  not have such a dependency, the load takes its data from the L1 data
  cache. Eventually, the prediction is verified. If an actual conflict is
  detected, the load and all succeeding instructions are re-executed.

af86ca4e30 ("bpf: Prevent memory disambiguation attack") tried to mitigate
this attack by sanitizing the memory locations through preemptive "fast"
(low latency) stores of zero prior to the actual "slow" (high latency) store
of a pointer value such that upon dependency misprediction the CPU then
speculatively executes the load of the pointer value and retrieves the zero
value instead of the attacker controlled scalar value previously stored at
that location, meaning, subsequent access in the speculative domain is then
redirected to the "zero page".

The sanitized preemptive store of zero prior to the actual "slow" store is
done through a simple ST instruction based on r10 (frame pointer) with
relative offset to the stack location that the verifier has been tracking
on the original used register for STX, which does not have to be r10. Thus,
there are no memory dependencies for this store, since it's only using r10
and immediate constant of zero; hence af86ca4e30 /assumed/ a low latency
operation.

However, a recent attack demonstrated that this mitigation is not sufficient
since the preemptive store of zero could also be turned into a "slow" store
and is thus bypassed as well:

  [...]
  // r2 = oob address (e.g. scalar)
  // r7 = pointer to map value
  31: (7b) *(u64 *)(r10 -16) = r2
  // r9 will remain "fast" register, r10 will become "slow" register below
  32: (bf) r9 = r10
  // JIT maps BPF reg to x86 reg:
  //  r9  -> r15 (callee saved)
  //  r10 -> rbp
  // train store forward prediction to break dependency link between both r9
  // and r10 by evicting them from the predictor's LRU table.
  33: (61) r0 = *(u32 *)(r7 +24576)
  34: (63) *(u32 *)(r7 +29696) = r0
  35: (61) r0 = *(u32 *)(r7 +24580)
  36: (63) *(u32 *)(r7 +29700) = r0
  37: (61) r0 = *(u32 *)(r7 +24584)
  38: (63) *(u32 *)(r7 +29704) = r0
  39: (61) r0 = *(u32 *)(r7 +24588)
  40: (63) *(u32 *)(r7 +29708) = r0
  [...]
  543: (61) r0 = *(u32 *)(r7 +25596)
  544: (63) *(u32 *)(r7 +30716) = r0
  // prepare call to bpf_ringbuf_output() helper. the latter will cause rbp
  // to spill to stack memory while r13/r14/r15 (all callee saved regs) remain
  // in hardware registers. rbp becomes slow due to push/pop latency. below is
  // disasm of bpf_ringbuf_output() helper for better visual context:
  //
  // ffffffff8117ee20: 41 54                 push   r12
  // ffffffff8117ee22: 55                    push   rbp
  // ffffffff8117ee23: 53                    push   rbx
  // ffffffff8117ee24: 48 f7 c1 fc ff ff ff  test   rcx,0xfffffffffffffffc
  // ffffffff8117ee2b: 0f 85 af 00 00 00     jne    ffffffff8117eee0 <-- jump taken
  // [...]
  // ffffffff8117eee0: 49 c7 c4 ea ff ff ff  mov    r12,0xffffffffffffffea
  // ffffffff8117eee7: 5b                    pop    rbx
  // ffffffff8117eee8: 5d                    pop    rbp
  // ffffffff8117eee9: 4c 89 e0              mov    rax,r12
  // ffffffff8117eeec: 41 5c                 pop    r12
  // ffffffff8117eeee: c3                    ret
  545: (18) r1 = map[id:4]
  547: (bf) r2 = r7
  548: (b7) r3 = 0
  549: (b7) r4 = 4
  550: (85) call bpf_ringbuf_output#194288
  // instruction 551 inserted by verifier    \
  551: (7a) *(u64 *)(r10 -16) = 0            | /both/ are now slow stores here
  // storing map value pointer r7 at fp-16   | since value of r10 is "slow".
  552: (7b) *(u64 *)(r10 -16) = r7           /
  // following "fast" read to the same memory location, but due to dependency
  // misprediction it will speculatively execute before insn 551/552 completes.
  553: (79) r2 = *(u64 *)(r9 -16)
  // in speculative domain contains attacker controlled r2. in non-speculative
  // domain this contains r7, and thus accesses r7 +0 below.
  554: (71) r3 = *(u8 *)(r2 +0)
  // leak r3

As can be seen, the current speculative store bypass mitigation which the
verifier inserts at line 551 is insufficient since /both/, the write of
the zero sanitation as well as the map value pointer are a high latency
instruction due to prior memory access via push/pop of r10 (rbp) in contrast
to the low latency read in line 553 as r9 (r15) which stays in hardware
registers. Thus, architecturally, fp-16 is r7, however, microarchitecturally,
fp-16 can still be r2.

Initial thoughts to address this issue was to track spilled pointer loads
from stack and enforce their load via LDX through r10 as well so that /both/
the preemptive store of zero /as well as/ the load use the /same/ register
such that a dependency is created between the store and load. However, this
option is not sufficient either since it can be bypassed as well under
speculation. An updated attack with pointer spill/fills now _all_ based on
r10 would look as follows:

  [...]
  // r2 = oob address (e.g. scalar)
  // r7 = pointer to map value
  [...]
  // longer store forward prediction training sequence than before.
  2062: (61) r0 = *(u32 *)(r7 +25588)
  2063: (63) *(u32 *)(r7 +30708) = r0
  2064: (61) r0 = *(u32 *)(r7 +25592)
  2065: (63) *(u32 *)(r7 +30712) = r0
  2066: (61) r0 = *(u32 *)(r7 +25596)
  2067: (63) *(u32 *)(r7 +30716) = r0
  // store the speculative load address (scalar) this time after the store
  // forward prediction training.
  2068: (7b) *(u64 *)(r10 -16) = r2
  // preoccupy the CPU store port by running sequence of dummy stores.
  2069: (63) *(u32 *)(r7 +29696) = r0
  2070: (63) *(u32 *)(r7 +29700) = r0
  2071: (63) *(u32 *)(r7 +29704) = r0
  2072: (63) *(u32 *)(r7 +29708) = r0
  2073: (63) *(u32 *)(r7 +29712) = r0
  2074: (63) *(u32 *)(r7 +29716) = r0
  2075: (63) *(u32 *)(r7 +29720) = r0
  2076: (63) *(u32 *)(r7 +29724) = r0
  2077: (63) *(u32 *)(r7 +29728) = r0
  2078: (63) *(u32 *)(r7 +29732) = r0
  2079: (63) *(u32 *)(r7 +29736) = r0
  2080: (63) *(u32 *)(r7 +29740) = r0
  2081: (63) *(u32 *)(r7 +29744) = r0
  2082: (63) *(u32 *)(r7 +29748) = r0
  2083: (63) *(u32 *)(r7 +29752) = r0
  2084: (63) *(u32 *)(r7 +29756) = r0
  2085: (63) *(u32 *)(r7 +29760) = r0
  2086: (63) *(u32 *)(r7 +29764) = r0
  2087: (63) *(u32 *)(r7 +29768) = r0
  2088: (63) *(u32 *)(r7 +29772) = r0
  2089: (63) *(u32 *)(r7 +29776) = r0
  2090: (63) *(u32 *)(r7 +29780) = r0
  2091: (63) *(u32 *)(r7 +29784) = r0
  2092: (63) *(u32 *)(r7 +29788) = r0
  2093: (63) *(u32 *)(r7 +29792) = r0
  2094: (63) *(u32 *)(r7 +29796) = r0
  2095: (63) *(u32 *)(r7 +29800) = r0
  2096: (63) *(u32 *)(r7 +29804) = r0
  2097: (63) *(u32 *)(r7 +29808) = r0
  2098: (63) *(u32 *)(r7 +29812) = r0
  // overwrite scalar with dummy pointer; same as before, also including the
  // sanitation store with 0 from the current mitigation by the verifier.
  2099: (7a) *(u64 *)(r10 -16) = 0         | /both/ are now slow stores here
  2100: (7b) *(u64 *)(r10 -16) = r7        | since store unit is still busy.
  // load from stack intended to bypass stores.
  2101: (79) r2 = *(u64 *)(r10 -16)
  2102: (71) r3 = *(u8 *)(r2 +0)
  // leak r3
  [...]

Looking at the CPU microarchitecture, the scheduler might issue loads (such
as seen in line 2101) before stores (line 2099,2100) because the load execution
units become available while the store execution unit is still busy with the
sequence of dummy stores (line 2069-2098). And so the load may use the prior
stored scalar from r2 at address r10 -16 for speculation. The updated attack
may work less reliable on CPU microarchitectures where loads and stores share
execution resources.

This concludes that the sanitizing with zero stores from af86ca4e30 ("bpf:
Prevent memory disambiguation attack") is insufficient. Moreover, the detection
of stack reuse from af86ca4e30 where previously data (STACK_MISC) has been
written to a given stack slot where a pointer value is now to be stored does
not have sufficient coverage as precondition for the mitigation either; for
several reasons outlined as follows:

 1) Stack content from prior program runs could still be preserved and is
    therefore not "random", best example is to split a speculative store
    bypass attack between tail calls, program A would prepare and store the
    oob address at a given stack slot and then tail call into program B which
    does the "slow" store of a pointer to the stack with subsequent "fast"
    read. From program B PoV such stack slot type is STACK_INVALID, and
    therefore also must be subject to mitigation.

 2) The STACK_SPILL must not be coupled to register_is_const(&stack->spilled_ptr)
    condition, for example, the previous content of that memory location could
    also be a pointer to map or map value. Without the fix, a speculative
    store bypass is not mitigated in such precondition and can then lead to
    a type confusion in the speculative domain leaking kernel memory near
    these pointer types.

While brainstorming on various alternative mitigation possibilities, we also
stumbled upon a retrospective from Chrome developers [0]:

  [...] For variant 4, we implemented a mitigation to zero the unused memory
  of the heap prior to allocation, which cost about 1% when done concurrently
  and 4% for scavenging. Variant 4 defeats everything we could think of. We
  explored more mitigations for variant 4 but the threat proved to be more
  pervasive and dangerous than we anticipated. For example, stack slots used
  by the register allocator in the optimizing compiler could be subject to
  type confusion, leading to pointer crafting. Mitigating type confusion for
  stack slots alone would have required a complete redesign of the backend of
  the optimizing compiler, perhaps man years of work, without a guarantee of
  completeness. [...]

From BPF side, the problem space is reduced, however, options are rather
limited. One idea that has been explored was to xor-obfuscate pointer spills
to the BPF stack:

  [...]
  // preoccupy the CPU store port by running sequence of dummy stores.
  [...]
  2106: (63) *(u32 *)(r7 +29796) = r0
  2107: (63) *(u32 *)(r7 +29800) = r0
  2108: (63) *(u32 *)(r7 +29804) = r0
  2109: (63) *(u32 *)(r7 +29808) = r0
  2110: (63) *(u32 *)(r7 +29812) = r0
  // overwrite scalar with dummy pointer; xored with random 'secret' value
  // of 943576462 before store ...
  2111: (b4) w11 = 943576462
  2112: (af) r11 ^= r7
  2113: (7b) *(u64 *)(r10 -16) = r11
  2114: (79) r11 = *(u64 *)(r10 -16)
  2115: (b4) w2 = 943576462
  2116: (af) r2 ^= r11
  // ... and restored with the same 'secret' value with the help of AX reg.
  2117: (71) r3 = *(u8 *)(r2 +0)
  [...]

While the above would not prevent speculation, it would make data leakage
infeasible by directing it to random locations. In order to be effective
and prevent type confusion under speculation, such random secret would have
to be regenerated for each store. The additional complexity involved for a
tracking mechanism that prevents jumps such that restoring spilled pointers
would not get corrupted is not worth the gain for unprivileged. Hence, the
fix in here eventually opted for emitting a non-public BPF_ST | BPF_NOSPEC
instruction which the x86 JIT translates into a lfence opcode. Inserting the
latter in between the store and load instruction is one of the mitigations
options [1]. The x86 instruction manual notes:

  [...] An LFENCE that follows an instruction that stores to memory might
  complete before the data being stored have become globally visible. [...]

The latter meaning that the preceding store instruction finished execution
and the store is at minimum guaranteed to be in the CPU's store queue, but
it's not guaranteed to be in that CPU's L1 cache at that point (globally
visible). The latter would only be guaranteed via sfence. So the load which
is guaranteed to execute after the lfence for that local CPU would have to
rely on store-to-load forwarding. [2], in section 2.3 on store buffers says:

  [...] For every store operation that is added to the ROB, an entry is
  allocated in the store buffer. This entry requires both the virtual and
  physical address of the target. Only if there is no free entry in the store
  buffer, the frontend stalls until there is an empty slot available in the
  store buffer again. Otherwise, the CPU can immediately continue adding
  subsequent instructions to the ROB and execute them out of order. On Intel
  CPUs, the store buffer has up to 56 entries. [...]

One small upside on the fix is that it lifts constraints from af86ca4e30
where the sanitize_stack_off relative to r10 must be the same when coming
from different paths. The BPF_ST | BPF_NOSPEC gets emitted after a BPF_STX
or BPF_ST instruction. This happens either when we store a pointer or data
value to the BPF stack for the first time, or upon later pointer spills.
The former needs to be enforced since otherwise stale stack data could be
leaked under speculation as outlined earlier. For non-x86 JITs the BPF_ST |
BPF_NOSPEC mapping is currently optimized away, but others could emit a
speculation barrier as well if necessary. For real-world unprivileged
programs e.g. generated by LLVM, pointer spill/fill is only generated upon
register pressure and LLVM only tries to do that for pointers which are not
used often. The program main impact will be the initial BPF_ST | BPF_NOSPEC
sanitation for the STACK_INVALID case when the first write to a stack slot
occurs e.g. upon map lookup. In future we might refine ways to mitigate
the latter cost.

  [0] https://arxiv.org/pdf/1902.05178.pdf
  [1] https://msrc-blog.microsoft.com/2018/05/21/analysis-and-mitigation-of-speculative-store-bypass-cve-2018-3639/
  [2] https://arxiv.org/pdf/1905.05725.pdf

Fixes: af86ca4e30 ("bpf: Prevent memory disambiguation attack")
Fixes: f7cf25b202 ("bpf: track spill/fill of constants")
Co-developed-by: Piotr Krysiuk <piotras@gmail.com>
Co-developed-by: Benedict Schlueter <benedict.schlueter@rub.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Piotr Krysiuk <piotras@gmail.com>
Signed-off-by: Benedict Schlueter <benedict.schlueter@rub.de>
Acked-by: Alexei Starovoitov <ast@kernel.org>
 2021-07-29 00:27:52 +02:00
David S. Miller
5af84df962 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 
Conflicts are simple overlapping changes.

Signed-off-by: David S. Miller <davem@davemloft.net>
 2021-07-23 16:13:06 +01:00
Daniel Borkmann
e042aa532c bpf: Fix pointer arithmetic mask tightening under state pruning 
In 7fedb63a83 ("bpf: Tighten speculative pointer arithmetic mask") we
narrowed the offset mask for unprivileged pointer arithmetic in order to
mitigate a corner case where in the speculative domain it is possible to
advance, for example, the map value pointer by up to value_size-1 out-of-
bounds in order to leak kernel memory via side-channel to user space.

The verifier's state pruning for scalars leaves one corner case open
where in the first verification path R_x holds an unknown scalar with an
aux->alu_limit of e.g. 7, and in a second verification path that same
register R_x, here denoted as R_x', holds an unknown scalar which has
tighter bounds and would thus satisfy range_within(R_x, R_x') as well as
tnum_in(R_x, R_x') for state pruning, yielding an aux->alu_limit of 3:
Given the second path fits the register constraints for pruning, the final
generated mask from aux->alu_limit will remain at 7. While technically
not wrong for the non-speculative domain, it would however be possible
to craft similar cases where the mask would be too wide as in 7fedb63a83.

One way to fix it is to detect the presence of unknown scalar map pointer
arithmetic and force a deeper search on unknown scalars to ensure that
we do not run into a masking mismatch.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
 2021-07-16 16:57:07 +02:00
Daniel Borkmann
59089a189e bpf: Remove superfluous aux sanitation on subprog rejection 
Follow-up to fe9a5ca7e3 ("bpf: Do not mark insn as seen under speculative
path verification"). The sanitize_insn_aux_data() helper does not serve a
particular purpose in today's code. The original intention for the helper
was that if function-by-function verification fails, a given program would
be cleared from temporary insn_aux_data[], and then its verification would
be re-attempted in the context of the main program a second time.

However, a failure in do_check_subprogs() will skip do_check_main() and
propagate the error to the user instead, thus such situation can never occur.
Given its interaction is not compatible to the Spectre v1 mitigation (due to
comparing aux->seen with env->pass_cnt), just remove sanitize_insn_aux_data()
to avoid future bugs in this area.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
 2021-07-16 16:57:07 +02:00
David S. Miller
82a1ffe57e Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 
Alexei Starovoitov says:

====================
pull-request: bpf-next 2021-07-15

The following pull-request contains BPF updates for your *net-next* tree.

We've added 45 non-merge commits during the last 15 day(s) which contain
a total of 52 files changed, 3122 insertions(+), 384 deletions(-).

The main changes are:

1) Introduce bpf timers, from Alexei.

2) Add sockmap support for unix datagram socket, from Cong.

3) Fix potential memleak and UAF in the verifier, from He.

4) Add bpf_get_func_ip helper, from Jiri.

5) Improvements to generic XDP mode, from Kumar.

6) Support for passing xdp_md to XDP programs in bpf_prog_run, from Zvi.
===================

Signed-off-by: David S. Miller <davem@davemloft.net>
 2021-07-15 22:40:10 -07:00
Jiri Olsa
9ffd9f3ff7 bpf: Add bpf_get_func_ip helper for kprobe programs 
Adding bpf_get_func_ip helper for BPF_PROG_TYPE_KPROBE programs,
so it's now possible to call bpf_get_func_ip from both kprobe and
kretprobe programs.

Taking the caller's address from 'struct kprobe::addr', which is
defined for both kprobe and kretprobe.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/bpf/20210714094400.396467-5-jolsa@kernel.org
 2021-07-15 17:59:09 -07:00
Jiri Olsa
9b99edcae5 bpf: Add bpf_get_func_ip helper for tracing programs 
Adding bpf_get_func_ip helper for BPF_PROG_TYPE_TRACING programs,
specifically for all trampoline attach types.

The trampoline's caller IP address is stored in (ctx - 8) address.
so there's no reason to actually call the helper, but rather fixup
the call instruction and return [ctx - 8] value directly.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210714094400.396467-4-jolsa@kernel.org
 2021-07-15 17:58:41 -07:00
Alexei Starovoitov
7ddc80a476 bpf: Teach stack depth check about async callbacks. 
Teach max stack depth checking algorithm about async callbacks
that don't increase bpf program stack size.
Also add sanity check that bpf_tail_call didn't sneak into async cb.
It's impossible, since PTR_TO_CTX is not available in async cb,
hence the program cannot contain bpf_tail_call(ctx,...);

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210715005417.78572-10-alexei.starovoitov@gmail.com
 2021-07-15 22:31:10 +02:00
Alexei Starovoitov
bfc6bb74e4 bpf: Implement verifier support for validation of async callbacks. 
bpf_for_each_map_elem() and bpf_timer_set_callback() helpers are relying on
PTR_TO_FUNC infra in the verifier to validate addresses to subprograms
and pass them into the helpers as function callbacks.
In case of bpf_for_each_map_elem() the callback is invoked synchronously
and the verifier treats it as a normal subprogram call by adding another
bpf_func_state and new frame in __check_func_call().
bpf_timer_set_callback() doesn't invoke the callback directly.
The subprogram will be called asynchronously from bpf_timer_cb().
Teach the verifier to validate such async callbacks as special kind
of jump by pushing verifier state into stack and let pop_stack() process it.

Special care needs to be taken during state pruning.
The call insn doing bpf_timer_set_callback has to be a prune_point.
Otherwise short timer callbacks might not have prune points in front of
bpf_timer_set_callback() which means is_state_visited() will be called
after this call insn is processed in __check_func_call(). Which means that
another async_cb state will be pushed to be walked later and the verifier
will eventually hit BPF_COMPLEXITY_LIMIT_JMP_SEQ limit.
Since push_async_cb() looks like another push_stack() branch the
infinite loop detection will trigger false positive. To recognize
this case mark such states as in_async_callback_fn.
To distinguish infinite loop in async callback vs the same callback called
with different arguments for different map and timer add async_entry_cnt
to bpf_func_state.

Enforce return zero from async callbacks.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210715005417.78572-9-alexei.starovoitov@gmail.com
 2021-07-15 22:31:10 +02:00
Alexei Starovoitov
86fc6ee6e2 bpf: Relax verifier recursion check. 
In the following bpf subprogram:
static int timer_cb(void *map, void *key, void *value)
{
    bpf_timer_set_callback(.., timer_cb);
}

the 'timer_cb' is a pointer to a function.
ld_imm64 insn is used to carry this pointer.
bpf_pseudo_func() returns true for such ld_imm64 insn.

Unlike bpf_for_each_map_elem() the bpf_timer_set_callback() is asynchronous.
Relax control flow check to allow such "recursion" that is seen as an infinite
loop by check_cfg(). The distinction between bpf_for_each_map_elem() the
bpf_timer_set_callback() is done in the follow up patch.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210715005417.78572-8-alexei.starovoitov@gmail.com
 2021-07-15 22:31:10 +02:00
Alexei Starovoitov
3e8ce29850 bpf: Prevent pointer mismatch in bpf_timer_init. 
bpf_timer_init() arguments are:
1. pointer to a timer (which is embedded in map element).
2. pointer to a map.
Make sure that pointer to a timer actually belongs to that map.

Use map_uid (which is unique id of inner map) to reject:
inner_map1 = bpf_map_lookup_elem(outer_map, key1)
inner_map2 = bpf_map_lookup_elem(outer_map, key2)
if (inner_map1 && inner_map2) {
    timer = bpf_map_lookup_elem(inner_map1);
    if (timer)
        // mismatch would have been allowed
        bpf_timer_init(timer, inner_map2);
}

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210715005417.78572-6-alexei.starovoitov@gmail.com
 2021-07-15 22:31:10 +02:00
Alexei Starovoitov
68134668c1 bpf: Add map side support for bpf timers. 
Restrict bpf timers to array, hash (both preallocated and kmalloced), and
lru map types. The per-cpu maps with timers don't make sense, since 'struct
bpf_timer' is a part of map value. bpf timers in per-cpu maps would mean that
the number of timers depends on number of possible cpus and timers would not be
accessible from all cpus. lpm map support can be added in the future.
The timers in inner maps are supported.

The bpf_map_update/delete_elem() helpers and sys_bpf commands cancel and free
bpf_timer in a given map element.

Similar to 'struct bpf_spin_lock' BTF is required and it is used to validate
that map element indeed contains 'struct bpf_timer'.

Make check_and_init_map_value() init both bpf_spin_lock and bpf_timer when
map element data is reused in preallocated htab and lru maps.

Teach copy_map_value() to support both bpf_spin_lock and bpf_timer in a single
map element. There could be one of each, but not more than one. Due to 'one
bpf_timer in one element' restriction do not support timers in global data,
since global data is a map of single element, but from bpf program side it's
seen as many global variables and restriction of single global timer would be
odd. The sys_bpf map_freeze and sys_mmap syscalls are not allowed on maps with
timers, since user space could have corrupted mmap element and crashed the
kernel. The maps with timers cannot be readonly. Due to these restrictions
search for bpf_timer in datasec BTF in case it was placed in the global data to
report clear error.

The previous patch allowed 'struct bpf_timer' as a first field in a map
element only. Relax this restriction.

Refactor lru map to s/bpf_lru_push_free/htab_lru_push_free/ to cancel and free
the timer when lru map deletes an element as a part of it eviction algorithm.

Make sure that bpf program cannot access 'struct bpf_timer' via direct load/store.
The timer operation are done through helpers only.
This is similar to 'struct bpf_spin_lock'.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210715005417.78572-5-alexei.starovoitov@gmail.com
 2021-07-15 22:31:10 +02:00
Alexei Starovoitov
b00628b1c7 bpf: Introduce bpf timers. 
Introduce 'struct bpf_timer { __u64 :64; __u64 :64; };' that can be embedded
in hash/array/lru maps as a regular field and helpers to operate on it:

// Initialize the timer.
// First 4 bits of 'flags' specify clockid.
// Only CLOCK_MONOTONIC, CLOCK_REALTIME, CLOCK_BOOTTIME are allowed.
long bpf_timer_init(struct bpf_timer *timer, struct bpf_map *map, int flags);

// Configure the timer to call 'callback_fn' static function.
long bpf_timer_set_callback(struct bpf_timer *timer, void *callback_fn);

// Arm the timer to expire 'nsec' nanoseconds from the current time.
long bpf_timer_start(struct bpf_timer *timer, u64 nsec, u64 flags);

// Cancel the timer and wait for callback_fn to finish if it was running.
long bpf_timer_cancel(struct bpf_timer *timer);

Here is how BPF program might look like:
struct map_elem {
    int counter;
    struct bpf_timer timer;
};

struct {
    __uint(type, BPF_MAP_TYPE_HASH);
    __uint(max_entries, 1000);
    __type(key, int);
    __type(value, struct map_elem);
} hmap SEC(".maps");

static int timer_cb(void *map, int *key, struct map_elem *val);
/* val points to particular map element that contains bpf_timer. */

SEC("fentry/bpf_fentry_test1")
int BPF_PROG(test1, int a)
{
    struct map_elem *val;
    int key = 0;

    val = bpf_map_lookup_elem(&hmap, &key);
    if (val) {
        bpf_timer_init(&val->timer, &hmap, CLOCK_REALTIME);
        bpf_timer_set_callback(&val->timer, timer_cb);
        bpf_timer_start(&val->timer, 1000 /* call timer_cb2 in 1 usec */, 0);
    }
}

This patch adds helper implementations that rely on hrtimers
to call bpf functions as timers expire.
The following patches add necessary safety checks.

Only programs with CAP_BPF are allowed to use bpf_timer.

The amount of timers used by the program is constrained by
the memcg recorded at map creation time.

The bpf_timer_init() helper needs explicit 'map' argument because inner maps
are dynamic and not known at load time. While the bpf_timer_set_callback() is
receiving hidden 'aux->prog' argument supplied by the verifier.

The prog pointer is needed to do refcnting of bpf program to make sure that
program doesn't get freed while the timer is armed. This approach relies on
"user refcnt" scheme used in prog_array that stores bpf programs for
bpf_tail_call. The bpf_timer_set_callback() will increment the prog refcnt which is
paired with bpf_timer_cancel() that will drop the prog refcnt. The
ops->map_release_uref is responsible for cancelling the timers and dropping
prog refcnt when user space reference to a map reaches zero.
This uref approach is done to make sure that Ctrl-C of user space process will
not leave timers running forever unless the user space explicitly pinned a map
that contained timers in bpffs.

bpf_timer_init() and bpf_timer_set_callback() will return -EPERM if map doesn't
have user references (is not held by open file descriptor from user space and
not pinned in bpffs).

The bpf_map_delete_elem() and bpf_map_update_elem() operations cancel
and free the timer if given map element had it allocated.
"bpftool map update" command can be used to cancel timers.

The 'struct bpf_timer' is explicitly __attribute__((aligned(8))) because
'__u64 :64' has 1 byte alignment of 8 byte padding.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210715005417.78572-4-alexei.starovoitov@gmail.com
 2021-07-15 22:31:10 +02:00
He Fengqing
75f0fc7b48 bpf: Fix potential memleak and UAF in the verifier. 
In bpf_patch_insn_data(), we first use the bpf_patch_insn_single() to
insert new instructions, then use adjust_insn_aux_data() to adjust
insn_aux_data. If the old env->prog have no enough room for new inserted
instructions, we use bpf_prog_realloc to construct new_prog and free the
old env->prog.

There have two errors here. First, if adjust_insn_aux_data() return
ENOMEM, we should free the new_prog. Second, if adjust_insn_aux_data()
return ENOMEM, bpf_patch_insn_data() will return NULL, and env->prog has
been freed in bpf_prog_realloc, but we will use it in bpf_check().

So in this patch, we make the adjust_insn_aux_data() never fails. In
bpf_patch_insn_data(), we first pre-malloc memory for the new
insn_aux_data, then call bpf_patch_insn_single() to insert new
instructions, at last call adjust_insn_aux_data() to adjust
insn_aux_data.

Fixes: 8041902dae ("bpf: adjust insn_aux_data when patching insns")
Signed-off-by: He Fengqing <hefengqing@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20210714101815.164322-1-hefengqing@huawei.com
 2021-07-14 18:31:24 -07:00
Daniel Borkmann
5dd0a6b858 bpf: Fix tail_call_reachable rejection for interpreter when jit failed 
During testing of f263a81451 ("bpf: Track subprog poke descriptors correctly
and fix use-after-free") under various failure conditions, for example, when
jit_subprogs() fails and tries to clean up the program to be run under the
interpreter, we ran into the following freeze:

  [...]
  #127/8 tailcall_bpf2bpf_3:FAIL
  [...]
  [   92.041251] BUG: KASAN: slab-out-of-bounds in ___bpf_prog_run+0x1b9d/0x2e20
  [   92.042408] Read of size 8 at addr ffff88800da67f68 by task test_progs/682
  [   92.043707]
  [   92.044030] CPU: 1 PID: 682 Comm: test_progs Tainted: G   O   5.13.0-53301-ge6c08cb33a30-dirty #87
  [   92.045542] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014
  [   92.046785] Call Trace:
  [   92.047171]  ? __bpf_prog_run_args64+0xc0/0xc0
  [   92.047773]  ? __bpf_prog_run_args32+0x8b/0xb0
  [   92.048389]  ? __bpf_prog_run_args64+0xc0/0xc0
  [   92.049019]  ? ktime_get+0x117/0x130
  [...] // few hundred [similar] lines more
  [   92.659025]  ? ktime_get+0x117/0x130
  [   92.659845]  ? __bpf_prog_run_args64+0xc0/0xc0
  [   92.660738]  ? __bpf_prog_run_args32+0x8b/0xb0
  [   92.661528]  ? __bpf_prog_run_args64+0xc0/0xc0
  [   92.662378]  ? print_usage_bug+0x50/0x50
  [   92.663221]  ? print_usage_bug+0x50/0x50
  [   92.664077]  ? bpf_ksym_find+0x9c/0xe0
  [   92.664887]  ? ktime_get+0x117/0x130
  [   92.665624]  ? kernel_text_address+0xf5/0x100
  [   92.666529]  ? __kernel_text_address+0xe/0x30
  [   92.667725]  ? unwind_get_return_address+0x2f/0x50
  [   92.668854]  ? ___bpf_prog_run+0x15d4/0x2e20
  [   92.670185]  ? ktime_get+0x117/0x130
  [   92.671130]  ? __bpf_prog_run_args64+0xc0/0xc0
  [   92.672020]  ? __bpf_prog_run_args32+0x8b/0xb0
  [   92.672860]  ? __bpf_prog_run_args64+0xc0/0xc0
  [   92.675159]  ? ktime_get+0x117/0x130
  [   92.677074]  ? lock_is_held_type+0xd5/0x130
  [   92.678662]  ? ___bpf_prog_run+0x15d4/0x2e20
  [   92.680046]  ? ktime_get+0x117/0x130
  [   92.681285]  ? __bpf_prog_run32+0x6b/0x90
  [   92.682601]  ? __bpf_prog_run64+0x90/0x90
  [   92.683636]  ? lock_downgrade+0x370/0x370
  [   92.684647]  ? mark_held_locks+0x44/0x90
  [   92.685652]  ? ktime_get+0x117/0x130
  [   92.686752]  ? lockdep_hardirqs_on+0x79/0x100
  [   92.688004]  ? ktime_get+0x117/0x130
  [   92.688573]  ? __cant_migrate+0x2b/0x80
  [   92.689192]  ? bpf_test_run+0x2f4/0x510
  [   92.689869]  ? bpf_test_timer_continue+0x1c0/0x1c0
  [   92.690856]  ? rcu_read_lock_bh_held+0x90/0x90
  [   92.691506]  ? __kasan_slab_alloc+0x61/0x80
  [   92.692128]  ? eth_type_trans+0x128/0x240
  [   92.692737]  ? __build_skb+0x46/0x50
  [   92.693252]  ? bpf_prog_test_run_skb+0x65e/0xc50
  [   92.693954]  ? bpf_prog_test_run_raw_tp+0x2d0/0x2d0
  [   92.694639]  ? __fget_light+0xa1/0x100
  [   92.695162]  ? bpf_prog_inc+0x23/0x30
  [   92.695685]  ? __sys_bpf+0xb40/0x2c80
  [   92.696324]  ? bpf_link_get_from_fd+0x90/0x90
  [   92.697150]  ? mark_held_locks+0x24/0x90
  [   92.698007]  ? lockdep_hardirqs_on_prepare+0x124/0x220
  [   92.699045]  ? finish_task_switch+0xe6/0x370
  [   92.700072]  ? lockdep_hardirqs_on+0x79/0x100
  [   92.701233]  ? finish_task_switch+0x11d/0x370
  [   92.702264]  ? __switch_to+0x2c0/0x740
  [   92.703148]  ? mark_held_locks+0x24/0x90
  [   92.704155]  ? __x64_sys_bpf+0x45/0x50
  [   92.705146]  ? do_syscall_64+0x35/0x80
  [   92.706953]  ? entry_SYSCALL_64_after_hwframe+0x44/0xae
  [...]

Turns out that the program rejection from e411901c0b ("bpf: allow for tailcalls
in BPF subprograms for x64 JIT") is buggy since env->prog->aux->tail_call_reachable
is never true. Commit ebf7d1f508 ("bpf, x64: rework pro/epilogue and tailcall
handling in JIT") added a tracker into check_max_stack_depth() which propagates
the tail_call_reachable condition throughout the subprograms. This info is then
assigned to the subprogram's func[i]->aux->tail_call_reachable. However, in the
case of the rejection check upon JIT failure, env->prog->aux->tail_call_reachable
is used. func[0]->aux->tail_call_reachable which represents the main program's
information did not propagate this to the outer env->prog->aux, though. Add this
propagation into check_max_stack_depth() where it needs to belong so that the
check can be done reliably.

Fixes: ebf7d1f508 ("bpf, x64: rework pro/epilogue and tailcall handling in JIT")
Fixes: e411901c0b ("bpf: allow for tailcalls in BPF subprograms for x64 JIT")
Co-developed-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/bpf/618c34e3163ad1a36b1e82377576a6081e182f25.1626123173.git.daniel@iogearbox.net
 2021-07-13 08:19:13 -07:00
John Fastabend
f263a81451 bpf: Track subprog poke descriptors correctly and fix use-after-free 
Subprograms are calling map_poke_track(), but on program release there is no
hook to call map_poke_untrack(). However, on program release, the aux memory
(and poke descriptor table) is freed even though we still have a reference to
it in the element list of the map aux data. When we run map_poke_run(), we then
end up accessing free'd memory, triggering KASAN in prog_array_map_poke_run():

  [...]
  [  402.824689] BUG: KASAN: use-after-free in prog_array_map_poke_run+0xc2/0x34e
  [  402.824698] Read of size 4 at addr ffff8881905a7940 by task hubble-fgs/4337
  [  402.824705] CPU: 1 PID: 4337 Comm: hubble-fgs Tainted: G          I       5.12.0+ #399
  [  402.824715] Call Trace:
  [  402.824719]  dump_stack+0x93/0xc2
  [  402.824727]  print_address_description.constprop.0+0x1a/0x140
  [  402.824736]  ? prog_array_map_poke_run+0xc2/0x34e
  [  402.824740]  ? prog_array_map_poke_run+0xc2/0x34e
  [  402.824744]  kasan_report.cold+0x7c/0xd8
  [  402.824752]  ? prog_array_map_poke_run+0xc2/0x34e
  [  402.824757]  prog_array_map_poke_run+0xc2/0x34e
  [  402.824765]  bpf_fd_array_map_update_elem+0x124/0x1a0
  [...]

The elements concerned are walked as follows:

    for (i = 0; i < elem->aux->size_poke_tab; i++) {
           poke = &elem->aux->poke_tab[i];
    [...]

The access to size_poke_tab is a 4 byte read, verified by checking offsets
in the KASAN dump:

  [  402.825004] The buggy address belongs to the object at ffff8881905a7800
                 which belongs to the cache kmalloc-1k of size 1024
  [  402.825008] The buggy address is located 320 bytes inside of
                 1024-byte region [ffff8881905a7800, ffff8881905a7c00)

The pahole output of bpf_prog_aux:

  struct bpf_prog_aux {
    [...]
    /* --- cacheline 5 boundary (320 bytes) --- */
    u32                        size_poke_tab;        /*   320     4 */
    [...]

In general, subprograms do not necessarily manage their own data structures.
For example, BTF func_info and linfo are just pointers to the main program
structure. This allows reference counting and cleanup to be done on the latter
which simplifies their management a bit. The aux->poke_tab struct, however,
did not follow this logic. The initial proposed fix for this use-after-free
bug further embedded poke data tracking into the subprogram with proper
reference counting. However, Daniel and Alexei questioned why we were treating
these objects special; I agree, its unnecessary. The fix here removes the per
subprogram poke table allocation and map tracking and instead simply points
the aux->poke_tab pointer at the main programs poke table. This way, map
tracking is simplified to the main program and we do not need to manage them
per subprogram.

This also means, bpf_prog_free_deferred(), which unwinds the program reference
counting and kfrees objects, needs to ensure that we don't try to double free
the poke_tab when free'ing the subprog structures. This is easily solved by
NULL'ing the poke_tab pointer. The second detail is to ensure that per
subprogram JIT logic only does fixups on poke_tab[] entries it owns. To do
this, we add a pointer in the poke structure to point at the subprogram value
so JITs can easily check while walking the poke_tab structure if the current
entry belongs to the current program. The aux pointer is stable and therefore
suitable for such comparison. On the jit_subprogs() error path, we omit
cleaning up the poke->aux field because these are only ever referenced from
the JIT side, but on error we will never make it to the JIT, so its fine to
leave them dangling. Removing these pointers would complicate the error path
for no reason. However, we do need to untrack all poke descriptors from the
main program as otherwise they could race with the freeing of JIT memory from
the subprograms. Lastly, a748c6975d ("bpf: propagate poke descriptors to
subprograms") had an off-by-one on the subprogram instruction index range
check as it was testing 'insn_idx >= subprog_start && insn_idx <= subprog_end'.
However, subprog_end is the next subprogram's start instruction.

Fixes: a748c6975d ("bpf: propagate poke descriptors to subprograms")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210707223848.14580-2-john.fastabend@gmail.com
 2021-07-09 12:08:27 +02:00
Jakub Kicinski
b6df00789e Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 
Trivial conflict in net/netfilter/nf_tables_api.c.

Duplicate fix in tools/testing/selftests/net/devlink_port_split.py
- take the net-next version.

skmsg, and L4 bpf - keep the bpf code but remove the flags
and err params.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
 2021-06-29 15:45:27 -07:00
John Fastabend
7506d211b9 bpf: Fix null ptr deref with mixed tail calls and subprogs 
The sub-programs prog->aux->poke_tab[] is populated in jit_subprogs() and
then used when emitting 'BPF_JMP|BPF_TAIL_CALL' insn->code from the
individual JITs. The poke_tab[] to use is stored in the insn->imm by
the code adding it to that array slot. The JIT then uses imm to find the
right entry for an individual instruction. In the x86 bpf_jit_comp.c
this is done by calling emit_bpf_tail_call_direct with the poke_tab[]
of the imm value.

However, we observed the below null-ptr-deref when mixing tail call
programs with subprog programs. For this to happen we just need to
mix bpf-2-bpf calls and tailcalls with some extra calls or instructions
that would be patched later by one of the fixup routines. So whats
happening?

Before the fixup_call_args() -- where the jit op is done -- various
code patching is done by do_misc_fixups(). This may increase the
insn count, for example when we patch map_lookup_up using map_gen_lookup
hook. This does two things. First, it means the instruction index,
insn_idx field, of a tail call instruction will move by a 'delta'.

In verifier code,

 struct bpf_jit_poke_descriptor desc = {
  .reason = BPF_POKE_REASON_TAIL_CALL,
  .tail_call.map = BPF_MAP_PTR(aux->map_ptr_state),
  .tail_call.key = bpf_map_key_immediate(aux),
  .insn_idx = i + delta,
 };

Then subprog start values subprog_info[i].start will be updated
with the delta and any poke descriptor index will also be updated
with the delta in adjust_poke_desc(). If we look at the adjust
subprog starts though we see its only adjusted when the delta
occurs before the new instructions,

        /* NOTE: fake 'exit' subprog should be updated as well. */
        for (i = 0; i <= env->subprog_cnt; i++) {
                if (env->subprog_info[i].start <= off)
                        continue;

Earlier subprograms are not changed because their start values
are not moved. But, adjust_poke_desc() does the offset + delta
indiscriminately. The result is poke descriptors are potentially
corrupted.

Then in jit_subprogs() we only populate the poke_tab[]
when the above insn_idx is less than the next subprogram start. From
above we corrupted our insn_idx so we might incorrectly assume a
poke descriptor is not used in a subprogram omitting it from the
subprogram. And finally when the jit runs it does the deref of poke_tab
when emitting the instruction and crashes with below. Because earlier
step omitted the poke descriptor.

The fix is straight forward with above context. Simply move same logic
from adjust_subprog_starts() into adjust_poke_descs() and only adjust
insn_idx when needed.

[   82.396354] bpf_testmod: version magic '5.12.0-rc2alu+ SMP preempt mod_unload ' should be '5.12.0+ SMP preempt mod_unload '
[   82.623001] loop10: detected capacity change from 0 to 8
[   88.487424] ==================================================================
[   88.487438] BUG: KASAN: null-ptr-deref in do_jit+0x184a/0x3290
[   88.487455] Write of size 8 at addr 0000000000000008 by task test_progs/5295
[   88.487471] CPU: 7 PID: 5295 Comm: test_progs Tainted: G          I       5.12.0+ #386
[   88.487483] Hardware name: Dell Inc. Precision 5820 Tower/002KVM, BIOS 1.9.2 01/24/2019
[   88.487490] Call Trace:
[   88.487498]  dump_stack+0x93/0xc2
[   88.487515]  kasan_report.cold+0x5f/0xd8
[   88.487530]  ? do_jit+0x184a/0x3290
[   88.487542]  do_jit+0x184a/0x3290
 ...
[   88.487709]  bpf_int_jit_compile+0x248/0x810
 ...
[   88.487765]  bpf_check+0x3718/0x5140
 ...
[   88.487920]  bpf_prog_load+0xa22/0xf10

Fixes: a748c6975d ("bpf: propagate poke descriptors to subprograms")
Reported-by: Jussi Maki <joamaki@gmail.com>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Daniel Borkmann <daniel@iogearbox.net>
 2021-06-22 14:46:39 -07:00
Jakub Kicinski
adc2e56ebe Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 
Trivial conflicts in net/can/isotp.c and
tools/testing/selftests/net/mptcp/mptcp_connect.sh

scaled_ppm_to_ppb() was moved from drivers/ptp/ptp_clock.c
to include/linux/ptp_clock_kernel.h in -next so re-apply
the fix there.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
 2021-06-18 19:47:02 -07:00
David S. Miller
a52171ae7b Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 
Daniel Borkmann says:

====================
pull-request: bpf-next 2021-06-17

The following pull-request contains BPF updates for your *net-next* tree.

We've added 50 non-merge commits during the last 25 day(s) which contain
a total of 148 files changed, 4779 insertions(+), 1248 deletions(-).

The main changes are:

1) BPF infrastructure to migrate TCP child sockets from a listener to another
   in the same reuseport group/map, from Kuniyuki Iwashima.

2) Add a provably sound, faster and more precise algorithm for tnum_mul() as
   noted in https://arxiv.org/abs/2105.05398, from Harishankar Vishwanathan.

3) Streamline error reporting changes in libbpf as planned out in the
   'libbpf: the road to v1.0' effort, from Andrii Nakryiko.

4) Add broadcast support to xdp_redirect_map(), from Hangbin Liu.

5) Extends bpf_map_lookup_and_delete_elem() functionality to 4 more map
   types, that is, {LRU_,PERCPU_,LRU_PERCPU_,}HASH, from Denis Salopek.

6) Support new LLVM relocations in libbpf to make them more linker friendly,
   also add a doc to describe the BPF backend relocations, from Yonghong Song.

7) Silence long standing KUBSAN complaints on register-based shifts in
   interpreter, from Daniel Borkmann and Eric Biggers.

8) Add dummy PT_REGS macros in libbpf to fail BPF program compilation when
   target arch cannot be determined, from Lorenz Bauer.

9) Extend AF_XDP to support large umems with 1M+ pages, from Magnus Karlsson.

10) Fix two minor libbpf tc BPF API issues, from Kumar Kartikeya Dwivedi.

11) Move libbpf BPF_SEQ_PRINTF/BPF_SNPRINTF macros that can be used by BPF
    programs to bpf_helpers.h header, from Florent Revest.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
 2021-06-17 11:54:56 -07:00
Daniel Borkmann
9183671af6 bpf: Fix leakage under speculation on mispredicted branches 
The verifier only enumerates valid control-flow paths and skips paths that
are unreachable in the non-speculative domain. And so it can miss issues
under speculative execution on mispredicted branches.

For example, a type confusion has been demonstrated with the following
crafted program:

  // r0 = pointer to a map array entry
  // r6 = pointer to readable stack slot
  // r9 = scalar controlled by attacker
  1: r0 = *(u64 *)(r0) // cache miss
  2: if r0 != 0x0 goto line 4
  3: r6 = r9
  4: if r0 != 0x1 goto line 6
  5: r9 = *(u8 *)(r6)
  6: // leak r9

Since line 3 runs iff r0 == 0 and line 5 runs iff r0 == 1, the verifier
concludes that the pointer dereference on line 5 is safe. But: if the
attacker trains both the branches to fall-through, such that the following
is speculatively executed ...

  r6 = r9
  r9 = *(u8 *)(r6)
  // leak r9

... then the program will dereference an attacker-controlled value and could
leak its content under speculative execution via side-channel. This requires
to mistrain the branch predictor, which can be rather tricky, because the
branches are mutually exclusive. However such training can be done at
congruent addresses in user space using different branches that are not
mutually exclusive. That is, by training branches in user space ...

  A:  if r0 != 0x0 goto line C
  B:  ...
  C:  if r0 != 0x0 goto line D
  D:  ...

... such that addresses A and C collide to the same CPU branch prediction
entries in the PHT (pattern history table) as those of the BPF program's
lines 2 and 4, respectively. A non-privileged attacker could simply brute
force such collisions in the PHT until observing the attack succeeding.

Alternative methods to mistrain the branch predictor are also possible that
avoid brute forcing the collisions in the PHT. A reliable attack has been
demonstrated, for example, using the following crafted program:

  // r0 = pointer to a [control] map array entry
  // r7 = *(u64 *)(r0 + 0), training/attack phase
  // r8 = *(u64 *)(r0 + 8), oob address
  // [...]
  // r0 = pointer to a [data] map array entry
  1: if r7 == 0x3 goto line 3
  2: r8 = r0
  // crafted sequence of conditional jumps to separate the conditional
  // branch in line 193 from the current execution flow
  3: if r0 != 0x0 goto line 5
  4: if r0 == 0x0 goto exit
  5: if r0 != 0x0 goto line 7
  6: if r0 == 0x0 goto exit
  [...]
  187: if r0 != 0x0 goto line 189
  188: if r0 == 0x0 goto exit
  // load any slowly-loaded value (due to cache miss in phase 3) ...
  189: r3 = *(u64 *)(r0 + 0x1200)
  // ... and turn it into known zero for verifier, while preserving slowly-
  // loaded dependency when executing:
  190: r3 &= 1
  191: r3 &= 2
  // speculatively bypassed phase dependency
  192: r7 += r3
  193: if r7 == 0x3 goto exit
  194: r4 = *(u8 *)(r8 + 0)
  // leak r4

As can be seen, in training phase (phase != 0x3), the condition in line 1
turns into false and therefore r8 with the oob address is overridden with
the valid map value address, which in line 194 we can read out without
issues. However, in attack phase, line 2 is skipped, and due to the cache
miss in line 189 where the map value is (zeroed and later) added to the
phase register, the condition in line 193 takes the fall-through path due
to prior branch predictor training, where under speculation, it'll load the
byte at oob address r8 (unknown scalar type at that point) which could then
be leaked via side-channel.

One way to mitigate these is to 'branch off' an unreachable path, meaning,
the current verification path keeps following the is_branch_taken() path
and we push the other branch to the verification stack. Given this is
unreachable from the non-speculative domain, this branch's vstate is
explicitly marked as speculative. This is needed for two reasons: i) if
this path is solely seen from speculative execution, then we later on still
want the dead code elimination to kick in in order to sanitize these
instructions with jmp-1s, and ii) to ensure that paths walked in the
non-speculative domain are not pruned from earlier walks of paths walked in
the speculative domain. Additionally, for robustness, we mark the registers
which have been part of the conditional as unknown in the speculative path
given there should be no assumptions made on their content.

The fix in here mitigates type confusion attacks described earlier due to
i) all code paths in the BPF program being explored and ii) existing
verifier logic already ensuring that given memory access instruction
references one specific data structure.

An alternative to this fix that has also been looked at in this scope was to
mark aux->alu_state at the jump instruction with a BPF_JMP_TAKEN state as
well as direction encoding (always-goto, always-fallthrough, unknown), such
that mixing of different always-* directions themselves as well as mixing of
always-* with unknown directions would cause a program rejection by the
verifier, e.g. programs with constructs like 'if ([...]) { x = 0; } else
{ x = 1; }' with subsequent 'if (x == 1) { [...] }'. For unprivileged, this
would result in only single direction always-* taken paths, and unknown taken
paths being allowed, such that the former could be patched from a conditional
jump to an unconditional jump (ja). Compared to this approach here, it would
have two downsides: i) valid programs that otherwise are not performing any
pointer arithmetic, etc, would potentially be rejected/broken, and ii) we are
required to turn off path pruning for unprivileged, where both can be avoided
in this work through pushing the invalid branch to the verification stack.

The issue was originally discovered by Adam and Ofek, and later independently
discovered and reported as a result of Benedict and Piotr's research work.

Fixes: b2157399cc ("bpf: prevent out-of-bounds speculation")
Reported-by: Adam Morrison <mad@cs.tau.ac.il>
Reported-by: Ofek Kirzner <ofekkir@gmail.com>
Reported-by: Benedict Schlueter <benedict.schlueter@rub.de>
Reported-by: Piotr Krysiuk <piotras@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Reviewed-by: Benedict Schlueter <benedict.schlueter@rub.de>
Reviewed-by: Piotr Krysiuk <piotras@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
 2021-06-14 23:06:10 +02:00
Daniel Borkmann
fe9a5ca7e3 bpf: Do not mark insn as seen under speculative path verification 
... in such circumstances, we do not want to mark the instruction as seen given
the goal is still to jmp-1 rewrite/sanitize dead code, if it is not reachable
from the non-speculative path verification. We do however want to verify it for
safety regardless.

With the patch as-is all the insns that have been marked as seen before the
patch will also be marked as seen after the patch (just with a potentially
different non-zero count). An upcoming patch will also verify paths that are
unreachable in the non-speculative domain, hence this extension is needed.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Reviewed-by: Benedict Schlueter <benedict.schlueter@rub.de>
Reviewed-by: Piotr Krysiuk <piotras@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
 2021-06-14 23:06:06 +02:00