Commit Graph

702 Commits

Author SHA1 Message Date
Alexey Gladkov
f3791f4df5 Fix UCOUNT_RLIMIT_SIGPENDING counter leak
We must properly handle an errors when we increase the rlimit counter
and the ucounts reference counter. We have to this with RCU protection
to prevent possible use-after-free that could occur due to concurrent
put_cred_rcu().

The following reproducer triggers the problem:

  $ cat testcase.sh
  case "${STEP:-0}" in
  0)
	ulimit -Si 1
	ulimit -Hi 1
	STEP=1 unshare -rU "$0"
	killall sleep
	;;
  1)
	for i in 1 2 3 4 5; do unshare -rU sleep 5 & done
	;;
  esac

with the KASAN report being along the lines of

  BUG: KASAN: use-after-free in put_ucounts+0x17/0xa0
  Write of size 4 at addr ffff8880045f031c by task swapper/2/0

  CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.13.0+ #19
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-alt4 04/01/2014
  Call Trace:
   <IRQ>
   put_ucounts+0x17/0xa0
   put_cred_rcu+0xd5/0x190
   rcu_core+0x3bf/0xcb0
   __do_softirq+0xe3/0x341
   irq_exit_rcu+0xbe/0xe0
   sysvec_apic_timer_interrupt+0x6a/0x90
   </IRQ>
   asm_sysvec_apic_timer_interrupt+0x12/0x20
   default_idle_call+0x53/0x130
   do_idle+0x311/0x3c0
   cpu_startup_entry+0x14/0x20
   secondary_startup_64_no_verify+0xc2/0xcb

  Allocated by task 127:
   kasan_save_stack+0x1b/0x40
   __kasan_kmalloc+0x7c/0x90
   alloc_ucounts+0x169/0x2b0
   set_cred_ucounts+0xbb/0x170
   ksys_unshare+0x24c/0x4e0
   __x64_sys_unshare+0x16/0x20
   do_syscall_64+0x37/0x70
   entry_SYSCALL_64_after_hwframe+0x44/0xae

  Freed by task 0:
   kasan_save_stack+0x1b/0x40
   kasan_set_track+0x1c/0x30
   kasan_set_free_info+0x20/0x30
   __kasan_slab_free+0xeb/0x120
   kfree+0xaa/0x460
   put_cred_rcu+0xd5/0x190
   rcu_core+0x3bf/0xcb0
   __do_softirq+0xe3/0x341

  The buggy address belongs to the object at ffff8880045f0300
   which belongs to the cache kmalloc-192 of size 192
  The buggy address is located 28 bytes inside of
   192-byte region [ffff8880045f0300, ffff8880045f03c0)
  The buggy address belongs to the page:
  page:000000008de0a388 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880045f0000 pfn:0x45f0
  flags: 0x100000000000200(slab|node=0|zone=1)
  raw: 0100000000000200 ffffea00000f4640 0000000a0000000a ffff888001042a00
  raw: ffff8880045f0000 000000008010000d 00000001ffffffff 0000000000000000
  page dumped because: kasan: bad access detected

  Memory state around the buggy address:
   ffff8880045f0200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
   ffff8880045f0280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
  >ffff8880045f0300: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                              ^
   ffff8880045f0380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
   ffff8880045f0400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ==================================================================
  Disabling lock debugging due to kernel taint

Fixes: d646969055 ("Reimplement RLIMIT_SIGPENDING on top of ucounts")
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-07-08 11:43:24 -07:00
Linus Torvalds
71bd934101 Merge branch 'akpm' (patches from Andrew)
Merge more updates from Andrew Morton:
 "190 patches.

  Subsystems affected by this patch series: mm (hugetlb, userfaultfd,
  vmscan, kconfig, proc, z3fold, zbud, ras, mempolicy, memblock,
  migration, thp, nommu, kconfig, madvise, memory-hotplug, zswap,
  zsmalloc, zram, cleanups, kfence, and hmm), procfs, sysctl, misc,
  core-kernel, lib, lz4, checkpatch, init, kprobes, nilfs2, hfs,
  signals, exec, kcov, selftests, compress/decompress, and ipc"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (190 commits)
  ipc/util.c: use binary search for max_idx
  ipc/sem.c: use READ_ONCE()/WRITE_ONCE() for use_global_lock
  ipc: use kmalloc for msg_queue and shmid_kernel
  ipc sem: use kvmalloc for sem_undo allocation
  lib/decompressors: remove set but not used variabled 'level'
  selftests/vm/pkeys: exercise x86 XSAVE init state
  selftests/vm/pkeys: refill shadow register after implicit kernel write
  selftests/vm/pkeys: handle negative sys_pkey_alloc() return code
  selftests/vm/pkeys: fix alloc_random_pkey() to make it really, really random
  kcov: add __no_sanitize_coverage to fix noinstr for all architectures
  exec: remove checks in __register_bimfmt()
  x86: signal: don't do sas_ss_reset() until we are certain that sigframe won't be abandoned
  hfsplus: report create_date to kstat.btime
  hfsplus: remove unnecessary oom message
  nilfs2: remove redundant continue statement in a while-loop
  kprobes: remove duplicated strong free_insn_page in x86 and s390
  init: print out unknown kernel parameters
  checkpatch: do not complain about positive return values starting with EPOLL
  checkpatch: improve the indented label test
  checkpatch: scripts/spdxcheck.py now requires python3
  ...
2021-07-02 12:08:10 -07:00
Al Viro
97c885d585 x86: signal: don't do sas_ss_reset() until we are certain that sigframe won't be abandoned
Currently we handle SS_AUTODISARM as soon as we have stored the altstack
settings into sigframe - that's the point when we have set the things up
for eventual sigreturn to restore the old settings.  And if we manage to
set the sigframe up (we are not done with that yet), everything's fine.
However, in case of failure we end up with sigframe-to-be abandoned and
SIGSEGV force-delivered.  And in that case we end up with inconsistent
rules - late failures have altstack reset, early ones do not.

It's trivial to get consistent behaviour - just handle SS_AUTODISARM once
we have set the sigframe up and are committed to entering the handler,
i.e.  in signal_delivered().

Link: https://lore.kernel.org/lkml/20200404170604.GN23230@ZenIV.linux.org.uk/
Link: https://github.com/ClangBuiltLinux/linux/issues/876
Link: https://lkml.kernel.org/r/20210422230846.1756380-1-ndesaulniers@google.com
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-07-01 11:06:06 -07:00
Linus Torvalds
c54b245d01 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull user namespace rlimit handling update from Eric Biederman:
 "This is the work mainly by Alexey Gladkov to limit rlimits to the
  rlimits of the user that created a user namespace, and to allow users
  to have stricter limits on the resources created within a user
  namespace."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  cred: add missing return error code when set_cred_ucounts() failed
  ucounts: Silence warning in dec_rlimit_ucounts
  ucounts: Set ucount_max to the largest positive value the type can hold
  kselftests: Add test to check for rlimit changes in different user namespaces
  Reimplement RLIMIT_MEMLOCK on top of ucounts
  Reimplement RLIMIT_SIGPENDING on top of ucounts
  Reimplement RLIMIT_MSGQUEUE on top of ucounts
  Reimplement RLIMIT_NPROC on top of ucounts
  Use atomic_t for ucounts reference counting
  Add a reference to ucounts for each cred
  Increase size of ucounts to atomic_long_t
2021-06-28 20:39:26 -07:00
Linus Torvalds
54a728dc5e Scheduler udpates for this cycle:
- Changes to core scheduling facilities:
 
     - Add "Core Scheduling" via CONFIG_SCHED_CORE=y, which enables
       coordinated scheduling across SMT siblings. This is a much
       requested feature for cloud computing platforms, to allow
       the flexible utilization of SMT siblings, without exposing
       untrusted domains to information leaks & side channels, plus
       to ensure more deterministic computing performance on SMT
       systems used by heterogenous workloads.
 
       There's new prctls to set core scheduling groups, which
       allows more flexible management of workloads that can share
       siblings.
 
     - Fix task->state access anti-patterns that may result in missed
       wakeups and rename it to ->__state in the process to catch new
       abuses.
 
  - Load-balancing changes:
 
      - Tweak newidle_balance for fair-sched, to improve
        'memcache'-like workloads.
 
      - "Age" (decay) average idle time, to better track & improve workloads
        such as 'tbench'.
 
      - Fix & improve energy-aware (EAS) balancing logic & metrics.
 
      - Fix & improve the uclamp metrics.
 
      - Fix task migration (taskset) corner case on !CONFIG_CPUSET.
 
      - Fix RT and deadline utilization tracking across policy changes
 
      - Introduce a "burstable" CFS controller via cgroups, which allows
        bursty CPU-bound workloads to borrow a bit against their future
        quota to improve overall latencies & batching. Can be tweaked
        via /sys/fs/cgroup/cpu/<X>/cpu.cfs_burst_us.
 
      - Rework assymetric topology/capacity detection & handling.
 
  - Scheduler statistics & tooling:
 
      - Disable delayacct by default, but add a sysctl to enable
        it at runtime if tooling needs it. Use static keys and
        other optimizations to make it more palatable.
 
      - Use sched_clock() in delayacct, instead of ktime_get_ns().
 
  - Misc cleanups and fixes.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
 -----BEGIN PGP SIGNATURE-----
 
 iQJFBAABCgAvFiEEBpT5eoXrXCwVQwEKEnMQ0APhK1gFAmDZcPoRHG1pbmdvQGtl
 cm5lbC5vcmcACgkQEnMQ0APhK1g3yw//WfhIqy7Psa9d/MBMjQDRGbTuO4+w22Dj
 vmWFU44Q4KJxQHWeIgUlrK+dzvYWvNmflUs2CUUOiDVzxFTHMIyBtL4qCBUbx4Ns
 vKAcB9wsWZge2o3WzZqpProRhdoRaSKw8egUr2q7rACVBkckY7eGP/OjWxXU8BdA
 b7D0LPWwuIBFfN4pFYeCDLn32Dqr9s6Chyj+ZecabdG7EE6Gu+f1diVcxy7JE/mc
 4WWL0D1RqdgpGrBEuMJIxPYekdrZiuy4jtEbztz5gbTBteN1cj3BLfqn0Pc/e6rO
 Vyuc5mXCAmzRVi18z6g6bsVl+IA/nrbErENB2OHOhOYtqiZxqGTd4GPWZszMyY17
 5AsEO5+5pcaBsy4gyp09qURggBu9zhJnMVmOI3rIHZkmkhwzc6uUJlyhDCTiFWOz
 3ZF3LjbZEyCKodMD8qMHbs3axIBpIfZqjzkvSKyFnvfXEGVytVse7NUuWtQ36u92
 GnURxVeYY1TDVXvE1Y8owNKMxknKQ6YRlypP7Dtbeo/qG6hShp0xmS7qDLDi0ybZ
 ZlK+bDECiVoDf3nvJo+8v5M82IJ3CBt4UYldeRJsa1YCK/FsbK8tp91fkEfnXVue
 +U6LPX0AmMpXacR5HaZfb3uBIKRw/QMdP/7RFtBPhpV6jqCrEmuqHnpPQiEVtxwO
 UmG7bt94Trk=
 =3VDr
 -----END PGP SIGNATURE-----

Merge tag 'sched-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler udpates from Ingo Molnar:

 - Changes to core scheduling facilities:

    - Add "Core Scheduling" via CONFIG_SCHED_CORE=y, which enables
      coordinated scheduling across SMT siblings. This is a much
      requested feature for cloud computing platforms, to allow the
      flexible utilization of SMT siblings, without exposing untrusted
      domains to information leaks & side channels, plus to ensure more
      deterministic computing performance on SMT systems used by
      heterogenous workloads.

      There are new prctls to set core scheduling groups, which allows
      more flexible management of workloads that can share siblings.

    - Fix task->state access anti-patterns that may result in missed
      wakeups and rename it to ->__state in the process to catch new
      abuses.

 - Load-balancing changes:

    - Tweak newidle_balance for fair-sched, to improve 'memcache'-like
      workloads.

    - "Age" (decay) average idle time, to better track & improve
      workloads such as 'tbench'.

    - Fix & improve energy-aware (EAS) balancing logic & metrics.

    - Fix & improve the uclamp metrics.

    - Fix task migration (taskset) corner case on !CONFIG_CPUSET.

    - Fix RT and deadline utilization tracking across policy changes

    - Introduce a "burstable" CFS controller via cgroups, which allows
      bursty CPU-bound workloads to borrow a bit against their future
      quota to improve overall latencies & batching. Can be tweaked via
      /sys/fs/cgroup/cpu/<X>/cpu.cfs_burst_us.

    - Rework assymetric topology/capacity detection & handling.

 - Scheduler statistics & tooling:

    - Disable delayacct by default, but add a sysctl to enable it at
      runtime if tooling needs it. Use static keys and other
      optimizations to make it more palatable.

    - Use sched_clock() in delayacct, instead of ktime_get_ns().

 - Misc cleanups and fixes.

* tag 'sched-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (72 commits)
  sched/doc: Update the CPU capacity asymmetry bits
  sched/topology: Rework CPU capacity asymmetry detection
  sched/core: Introduce SD_ASYM_CPUCAPACITY_FULL sched_domain flag
  psi: Fix race between psi_trigger_create/destroy
  sched/fair: Introduce the burstable CFS controller
  sched/uclamp: Fix uclamp_tg_restrict()
  sched/rt: Fix Deadline utilization tracking during policy change
  sched/rt: Fix RT utilization tracking during policy change
  sched: Change task_struct::state
  sched,arch: Remove unused TASK_STATE offsets
  sched,timer: Use __set_current_state()
  sched: Add get_current_state()
  sched,perf,kvm: Fix preemption condition
  sched: Introduce task_is_running()
  sched: Unbreak wakeups
  sched/fair: Age the average idle time
  sched/cpufreq: Consider reduced CPU capacity in energy calculation
  sched/fair: Take thermal pressure into account while estimating energy
  thermal/cpufreq_cooling: Update offline CPUs per-cpu thermal_pressure
  sched/fair: Return early from update_tg_cfs_load() if delta == 0
  ...
2021-06-28 12:14:19 -07:00
Linus Torvalds
b4b27b9eed Revert "signal: Allow tasks to cache one sigqueue struct"
This reverts commits 4bad58ebc8 (and
399f8dd9a8, which tried to fix it).

I do not believe these are correct, and I'm about to release 5.13, so am
reverting them out of an abundance of caution.

The locking is odd, and appears broken.

On the allocation side (in __sigqueue_alloc()), the locking is somewhat
straightforward: it depends on sighand->siglock.  Since one caller
doesn't hold that lock, it further then tests 'sigqueue_flags' to avoid
the case with no locks held.

On the freeing side (in sigqueue_cache_or_free()), there is no locking
at all, and the logic instead depends on 'current' being a single
thread, and not able to race with itself.

To make things more exciting, there's also the data race between freeing
a signal and allocating one, which is handled by using WRITE_ONCE() and
READ_ONCE(), and being mutually exclusive wrt the initial state (ie
freeing will only free if the old state was NULL, while allocating will
obviously only use the value if it was non-NULL, so only one or the
other will actually act on the value).

However, while the free->alloc paths do seem mutually exclusive thanks
to just the data value dependency, it's not clear what the memory
ordering constraints are on it.  Could writes from the previous
allocation possibly be delayed and seen by the new allocation later,
causing logical inconsistencies?

So it's all very exciting and unusual.

And in particular, it seems that the freeing side is incorrect in
depending on "current" being single-threaded.  Yes, 'current' is a
single thread, but in the presense of asynchronous events even a single
thread can have data races.

And such asynchronous events can and do happen, with interrupts causing
signals to be flushed and thus free'd (for example - sending a
SIGCONT/SIGSTOP can happen from interrupt context, and can flush
previously queued process control signals).

So regardless of all the other questions about the memory ordering and
locking for this new cached allocation, the sigqueue_cache_or_free()
assumptions seem to be fundamentally incorrect.

It may be that people will show me the errors of my ways, and tell me
why this is all safe after all.  We can reinstate it if so.  But my
current belief is that the WRITE_ONCE() that sets the cached entry needs
to be a smp_store_release(), and the READ_ONCE() that finds a cached
entry needs to be a smp_load_acquire() to handle memory ordering
correctly.

And the sequence in sigqueue_cache_or_free() would need to either use a
lock or at least be interrupt-safe some way (perhaps by using something
like the percpu 'cmpxchg': it doesn't need to be SMP-safe, but like the
percpu operations it needs to be interrupt-safe).

Fixes: 399f8dd9a8 ("signal: Prevent sigqueue caching after task got released")
Fixes: 4bad58ebc8 ("signal: Allow tasks to cache one sigqueue struct")
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-06-27 13:32:54 -07:00
Thomas Gleixner
399f8dd9a8 signal: Prevent sigqueue caching after task got released
syzbot reported a memory leak related to sigqueue caching.

The assumption that a task cannot cache a sigqueue after the signal handler
has been dropped and exit_task_sigqueue_cache() has been invoked turns out
to be wrong.

Such a task can still invoke release_task(other_task), which cleans up the
signals of 'other_task' and ends up in sigqueue_cache_or_free(), which in
turn will cache the signal because task->sigqueue_cache is NULL. That's
obviously bogus because nothing will free the cached signal of that task
anymore, so the cached item is leaked.

This happens when e.g. the last non-leader thread exits and reaps the
zombie leader.

Prevent this by setting tsk::sigqueue_cache to an error pointer value in
exit_task_sigqueue_cache() which forces any subsequent invocation of
sigqueue_cache_or_free() from that task to hand the sigqueue back to the
kmemcache.

Add comments to all relevant places.

Fixes: 4bad58ebc8 ("signal: Allow tasks to cache one sigqueue struct")
Reported-by: syzbot+0bac5fec63d4f399ba98@syzkaller.appspotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/878s32g6j5.ffs@nanos.tec.linutronix.de
2021-06-22 15:55:41 +02:00
Peter Zijlstra
b03fbd4ff2 sched: Introduce task_is_running()
Replace a bunch of 'p->state == TASK_RUNNING' with a new helper:
task_is_running(p).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210611082838.222401495@infradead.org
2021-06-18 11:43:07 +02:00
Linus Torvalds
a0e31f3a38 Merge branch 'for-v5.13-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull siginfo fix from Eric Biederman:
 "During the merge window an issue with si_perf and the siginfo ABI came
  up. The alpha and sparc siginfo structure layout had changed with the
  addition of SIGTRAP TRAP_PERF and the new field si_perf.

  The reason only alpha and sparc were affected is that they are the
  only architectures that use si_trapno.

  Looking deeper it was discovered that si_trapno is used for only a few
  select signals on alpha and sparc, and that none of the other
  _sigfault fields past si_addr are used at all. Which means technically
  no regression on alpha and sparc.

  While the alignment concerns might be dismissed the abuse of si_errno
  by SIGTRAP TRAP_PERF does have the potential to cause regressions in
  existing userspace.

  While we still have time before userspace starts using and depending
  on the new definition siginfo for SIGTRAP TRAP_PERF this set of
  changes cleans up siginfo_t.

   - The si_trapno field is demoted from magic alpha and sparc status
     and made an ordinary union member of the _sigfault member of
     siginfo_t. Without moving it of course.

   - si_perf is replaced with si_perf_data and si_perf_type ending the
     abuse of si_errno.

   - Unnecessary additions to signalfd_siginfo are removed"

* 'for-v5.13-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  signalfd: Remove SIL_PERF_EVENT fields from signalfd_siginfo
  signal: Deliver all of the siginfo perf data in _perf
  signal: Factor force_sig_perf out of perf_sigtrap
  signal: Implement SIL_FAULT_TRAPNO
  siginfo: Move si_trapno inside the union inside _si_fault
2021-05-21 06:12:52 -10:00
Eric W. Biederman
0683b53197 signal: Deliver all of the siginfo perf data in _perf
Don't abuse si_errno and deliver all of the perf data in _perf member
of siginfo_t.

Note: The data field in the perf data structures in a u64 to allow a
pointer to be encoded without needed to implement a 32bit and 64bit
version of the same structure.  There already exists a 32bit and 64bit
versions siginfo_t, and the 32bit version can not include a 64bit
member as it only has 32bit alignment.  So unsigned long is used in
siginfo_t instead of a u64 as unsigned long can encode a pointer on
all architectures linux supports.

v1: https://lkml.kernel.org/r/m11rarqqx2.fsf_-_@fess.ebiederm.org
v2: https://lkml.kernel.org/r/20210503203814.25487-10-ebiederm@xmission.com
v3: https://lkml.kernel.org/r/20210505141101.11519-11-ebiederm@xmission.com
Link: https://lkml.kernel.org/r/20210517195748.8880-4-ebiederm@xmission.com
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-05-18 16:20:54 -05:00
Eric W. Biederman
af5eeab7e8 signal: Factor force_sig_perf out of perf_sigtrap
Separate filling in siginfo for TRAP_PERF from deciding that
siginal needs to be sent.

There are enough little details that need to be correct when
properly filling in siginfo_t that it is easy to make mistakes
if filling in the siginfo_t is in the same function with other
logic.  So factor out force_sig_perf to reduce the cognative
load of on reviewers, maintainers and implementors.

v1: https://lkml.kernel.org/r/m17dkjqqxz.fsf_-_@fess.ebiederm.org
v2: https://lkml.kernel.org/r/20210505141101.11519-10-ebiederm@xmission.com
Link: https://lkml.kernel.org/r/20210517195748.8880-3-ebiederm@xmission.com
Reviewed-by: Marco Elver <elver@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-05-18 16:20:54 -05:00
Eric W. Biederman
9abcabe311 signal: Implement SIL_FAULT_TRAPNO
Now that si_trapno is part of the union in _si_fault and available on
all architectures, add SIL_FAULT_TRAPNO and update siginfo_layout to
return SIL_FAULT_TRAPNO when the code assumes si_trapno is valid.

There is room for future changes to reduce when si_trapno is valid but
this is all that is needed to make si_trapno and the other members of
the the union in _sigfault mutually exclusive.

Update the code that uses siginfo_layout to deal with SIL_FAULT_TRAPNO
and have the same code ignore si_trapno in in all other cases.

v1: https://lkml.kernel.org/r/m1o8dvs7s7.fsf_-_@fess.ebiederm.org
v2: https://lkml.kernel.org/r/20210505141101.11519-6-ebiederm@xmission.com
Link: https://lkml.kernel.org/r/20210517195748.8880-2-ebiederm@xmission.com
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-05-18 16:20:34 -05:00
Eric W. Biederman
add0b32ef9 siginfo: Move si_trapno inside the union inside _si_fault
It turns out that linux uses si_trapno very sparingly, and as such it
can be considered extra information for a very narrow selection of
signals, rather than information that is present with every fault
reported in siginfo.

As such move si_trapno inside the union inside of _si_fault.  This
results in no change in placement, and makes it eaiser
to extend _si_fault in the future as this reduces the number of
special cases.  In particular with si_trapno included in the union it
is no longer a concern that the union must be pointer aligned on most
architectures because the union follows immediately after si_addr
which is a pointer.

This change results in a difference in siginfo field placement on
sparc and alpha for the fields si_addr_lsb, si_lower, si_upper,
si_pkey, and si_perf.  These architectures do not implement the
signals that would use si_addr_lsb, si_lower, si_upper, si_pkey, and
si_perf.  Further these architecture have not yet implemented the
userspace that would use si_perf.

The point of this change is in fact to correct these placement issues
before sparc or alpha grow userspace that cares.  This change was
discussed[1] and the agreement is that this change is currently safe.

[1]: https://lkml.kernel.org/r/CAK8P3a0+uKYwL1NhY6Hvtieghba2hKYGD6hcKx5n8=4Gtt+pHA@mail.gmail.com
Acked-by: Marco Elver <elver@google.com>
v1: https://lkml.kernel.org/r/m1tunns7yf.fsf_-_@fess.ebiederm.org
v2: https://lkml.kernel.org/r/20210505141101.11519-5-ebiederm@xmission.com
Link: https://lkml.kernel.org/r/20210517195748.8880-1-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-05-18 16:17:03 -05:00
Alexey Gladkov
d646969055 Reimplement RLIMIT_SIGPENDING on top of ucounts
The rlimit counter is tied to uid in the user_namespace. This allows
rlimit values to be specified in userns even if they are already
globally exceeded by the user. However, the value of the previous
user_namespaces cannot be exceeded.

Changelog

v11:
* Revert most of changes to fix performance issues.

v10:
* Fix memory leak on get_ucounts failure.

Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://lkml.kernel.org/r/df9d7764dddd50f28616b7840de74ec0f81711a8.1619094428.git.legion@kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2021-04-30 14:14:02 -05:00
Linus Torvalds
16b3d0cf5b Scheduler updates for this cycle are:
- Clean up SCHED_DEBUG: move the decades old mess of sysctl, procfs and debugfs interfaces
    to a unified debugfs interface.
 
  - Signals: Allow caching one sigqueue object per task, to improve performance & latencies.
 
  - Improve newidle_balance() irq-off latencies on systems with a large number of CPU cgroups.
 
  - Improve energy-aware scheduling
 
  - Improve the PELT metrics for certain workloads
 
  - Reintroduce select_idle_smt() to improve load-balancing locality - but without the previous
    regressions
 
  - Add 'scheduler latency debugging': warn after long periods of pending need_resched. This
    is an opt-in feature that requires the enabling of the LATENCY_WARN scheduler feature,
    or the use of the resched_latency_warn_ms=xx boot parameter.
 
  - CPU hotplug fixes for HP-rollback, and for the 'fail' interface. Fix remaining
    balance_push() vs. hotplug holes/races
 
  - PSI fixes, plus allow /proc/pressure/ files to be written by CAP_SYS_RESOURCE tasks as well
 
  - Fix/improve various load-balancing corner cases vs. capacity margins
 
  - Fix sched topology on systems with NUMA diameter of 3 or above
 
  - Fix PF_KTHREAD vs to_kthread() race
 
  - Minor rseq optimizations
 
  - Misc cleanups, optimizations, fixes and smaller updates
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
 -----BEGIN PGP SIGNATURE-----
 
 iQJFBAABCgAvFiEEBpT5eoXrXCwVQwEKEnMQ0APhK1gFAmCJInsRHG1pbmdvQGtl
 cm5lbC5vcmcACgkQEnMQ0APhK1i5XxAArh0b+fwXlkVGzTUly7HQjhU7lFbChnmF
 h6ToyNLi6pXoZ14VC/WoRIME+RzK3gmw9cEFaSLVPxbkbekTcyWS78kqmcg1/j2v
 kO/20QhXobiIxVskYfoMmqSavZ5mKhMWBqtFXkCuYfxwGylas0VVdh3AZLJ7N21G
 WEoFh99pVULwWnPHxM2ZQ87Ex9BkGKbsBTswxWpprCfXLqD0N2hHlABpwJP78zRf
 VniWFOcC7lslILCFawb7CqGgAwbgV85nDRS4QCuCKisrkFywvjJrEeu/W+h1NfhF
 d6ves/osNdEAM1DSALoxwEA42An8l8xh8NyJnl8JZV00LW0DM108O5/7pf5Zcryc
 RHV3RxA7skgezBh5uThvo60QzNK+kVMatI4qpQEHxLE52CaDl/fBu1Cgb/VUxnIl
 AEBfyiFbk+skHpuMFKtl30Tx3M+yJKMTzFPd4kYjHYGEDwtAcXcB3dJQW48A79i3
 H3IWcDcXpk5Rjo2UZmaXdt/qlj7mP6U0xdOUq8ZK6JOC4uY9skszVGsfuNN9QQ5u
 2E2YKKVrGFoQydl4C8R6A7axL2VzIJszHFZNipd8E3YOyW7PWRAkr02tOOkBTj8N
 dLMcNM7aPJWqEYiEIjEzGQN20pweJ1dRA29LDuOswKh+7W2bWTQFh6F2Q8Haansc
 RVg5PDzl+Mc=
 =E7mz
 -----END PGP SIGNATURE-----

Merge tag 'sched-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - Clean up SCHED_DEBUG: move the decades old mess of sysctl, procfs and
   debugfs interfaces to a unified debugfs interface.

 - Signals: Allow caching one sigqueue object per task, to improve
   performance & latencies.

 - Improve newidle_balance() irq-off latencies on systems with a large
   number of CPU cgroups.

 - Improve energy-aware scheduling

 - Improve the PELT metrics for certain workloads

 - Reintroduce select_idle_smt() to improve load-balancing locality -
   but without the previous regressions

 - Add 'scheduler latency debugging': warn after long periods of pending
   need_resched. This is an opt-in feature that requires the enabling of
   the LATENCY_WARN scheduler feature, or the use of the
   resched_latency_warn_ms=xx boot parameter.

 - CPU hotplug fixes for HP-rollback, and for the 'fail' interface. Fix
   remaining balance_push() vs. hotplug holes/races

 - PSI fixes, plus allow /proc/pressure/ files to be written by
   CAP_SYS_RESOURCE tasks as well

 - Fix/improve various load-balancing corner cases vs. capacity margins

 - Fix sched topology on systems with NUMA diameter of 3 or above

 - Fix PF_KTHREAD vs to_kthread() race

 - Minor rseq optimizations

 - Misc cleanups, optimizations, fixes and smaller updates

* tag 'sched-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (61 commits)
  cpumask/hotplug: Fix cpu_dying() state tracking
  kthread: Fix PF_KTHREAD vs to_kthread() race
  sched/debug: Fix cgroup_path[] serialization
  sched,psi: Handle potential task count underflow bugs more gracefully
  sched: Warn on long periods of pending need_resched
  sched/fair: Move update_nohz_stats() to the CONFIG_NO_HZ_COMMON block to simplify the code & fix an unused function warning
  sched/debug: Rename the sched_debug parameter to sched_verbose
  sched,fair: Alternative sched_slice()
  sched: Move /proc/sched_debug to debugfs
  sched,debug: Convert sysctl sched_domains to debugfs
  debugfs: Implement debugfs_create_str()
  sched,preempt: Move preempt_dynamic to debug.c
  sched: Move SCHED_DEBUG sysctl to debugfs
  sched: Don't make LATENCYTOP select SCHED_DEBUG
  sched: Remove sched_schedstats sysctl out from under SCHED_DEBUG
  sched/numa: Allow runtime enabling/disabling of NUMA balance without SCHED_DEBUG
  sched: Use cpu_dying() to fix balance_push vs hotplug-rollback
  cpumask: Introduce DYING mask
  cpumask: Make cpu_{online,possible,present,active}() inline
  rseq: Optimise rseq_get_rseq_cs() and clear_rseq_cs()
  ...
2021-04-28 13:33:57 -07:00
Linus Torvalds
42dec9a936 Perf events changes in this cycle were:
- Improve Intel uncore PMU support:
 
      - Parse uncore 'discovery tables' - a new hardware capability enumeration method
        introduced on the latest Intel platforms. This table is in a well-defined PCI
        namespace location and is read via MMIO. It is organized in an rbtree.
 
        These uncore tables will allow the discovery of standard counter blocks, but
        fancier counters still need to be enumerated explicitly.
 
      - Add Alder Lake support
 
      - Improve IIO stacks to PMON mapping support on Skylake servers
 
  - Add Intel Alder Lake PMU support - which requires the introduction of 'hybrid' CPUs
    and PMUs. Alder Lake is a mix of Golden Cove ('big') and Gracemont ('small' - Atom derived)
    cores.
 
    The CPU-side feature set is entirely symmetrical - but on the PMU side there's
    core type dependent PMU functionality.
 
  - Reduce data loss with CPU level hardware tracing on Intel PT / AUX profiling, by
    fixing the AUX allocation watermark logic.
 
  - Improve ring buffer allocation on NUMA systems
 
  - Put 'struct perf_event' into their separate kmem_cache pool
 
  - Add support for synchronous signals for select perf events. The immediate motivation
    is to support low-overhead sampling-based race detection for user-space code. The
    feature consists of the following main changes:
 
     - Add thread-only event inheritance via perf_event_attr::inherit_thread, which limits
       inheritance of events to CLONE_THREAD.
 
     - Add the ability for events to not leak through exec(), via perf_event_attr::remove_on_exec.
 
     - Allow the generation of SIGTRAP via perf_event_attr::sigtrap, extend siginfo with an u64
       ::si_perf, and add the breakpoint information to ::si_addr and ::si_perf if the event is
       PERF_TYPE_BREAKPOINT.
 
    The siginfo support is adequate for breakpoints right now - but the new field can be used
    to introduce support for other types of metadata passed over siginfo as well.
 
  - Misc fixes, cleanups and smaller updates.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
 -----BEGIN PGP SIGNATURE-----
 
 iQJFBAABCgAvFiEEBpT5eoXrXCwVQwEKEnMQ0APhK1gFAmCJGpERHG1pbmdvQGtl
 cm5lbC5vcmcACgkQEnMQ0APhK1j9zBAAuVbG2snV6SBSdXLhQcM66N3NckOXvSY5
 QjjhQcuwJQEK/NJB3266K5d8qSmdyRBsWf3GCsrmyBT67P1V28K44Pu7oCV0UDtf
 mpVRjEP0oR7hNsANSSgo8Fa4ZD7H5waX7dK7925Tvw8By3mMoZoddiD/84WJHhxO
 NDF+GRFaRj+/dpbhV8cdCoXTjYdkC36vYuZs3b9lu0tS9D/AJgsNy7TinLvO02Cs
 5peP+2y29dgvCXiGBiuJtEA6JyGnX3nUJCvfOZZ/DWDc3fdduARlRrc5Aiq4n/wY
 UdSkw1VTZBlZ1wMSdmHQVeC5RIH3uWUtRoNqy0Yc90lBm55AQ0EENwIfWDUDC5zy
 USdBqWTNWKMBxlEilUIyqKPQK8LW/31TRzqy8BWKPNcZt5yP5YS1SjAJRDDjSwL/
 I+OBw1vjLJamYh8oNiD5b+VLqNQba81jFASfv+HVWcULumnY6ImECCpkg289Fkpi
 BVR065boifJDlyENXFbvTxyMBXQsZfA+EhtxG7ju2Ni+TokBbogyCb3L2injPt9g
 7jjtTOqmfad4gX1WSc+215iYZMkgECcUd9E+BfOseEjBohqlo7yNKIfYnT8mE/Xq
 nb7eHjyvLiE8tRtZ+7SjsujOMHv9LhWFAbSaxU/kEVzpkp0zyd6mnnslDKaaHLhz
 goUMOL/D0lg=
 =NhQ7
 -----END PGP SIGNATURE-----

Merge tag 'perf-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull perf event updates from Ingo Molnar:

 - Improve Intel uncore PMU support:

     - Parse uncore 'discovery tables' - a new hardware capability
       enumeration method introduced on the latest Intel platforms. This
       table is in a well-defined PCI namespace location and is read via
       MMIO. It is organized in an rbtree.

       These uncore tables will allow the discovery of standard counter
       blocks, but fancier counters still need to be enumerated
       explicitly.

     - Add Alder Lake support

     - Improve IIO stacks to PMON mapping support on Skylake servers

 - Add Intel Alder Lake PMU support - which requires the introduction of
   'hybrid' CPUs and PMUs. Alder Lake is a mix of Golden Cove ('big')
   and Gracemont ('small' - Atom derived) cores.

   The CPU-side feature set is entirely symmetrical - but on the PMU
   side there's core type dependent PMU functionality.

 - Reduce data loss with CPU level hardware tracing on Intel PT / AUX
   profiling, by fixing the AUX allocation watermark logic.

 - Improve ring buffer allocation on NUMA systems

 - Put 'struct perf_event' into their separate kmem_cache pool

 - Add support for synchronous signals for select perf events. The
   immediate motivation is to support low-overhead sampling-based race
   detection for user-space code. The feature consists of the following
   main changes:

     - Add thread-only event inheritance via
       perf_event_attr::inherit_thread, which limits inheritance of
       events to CLONE_THREAD.

     - Add the ability for events to not leak through exec(), via
       perf_event_attr::remove_on_exec.

     - Allow the generation of SIGTRAP via perf_event_attr::sigtrap,
       extend siginfo with an u64 ::si_perf, and add the breakpoint
       information to ::si_addr and ::si_perf if the event is
       PERF_TYPE_BREAKPOINT.

   The siginfo support is adequate for breakpoints right now - but the
   new field can be used to introduce support for other types of
   metadata passed over siginfo as well.

 - Misc fixes, cleanups and smaller updates.

* tag 'perf-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (53 commits)
  signal, perf: Add missing TRAP_PERF case in siginfo_layout()
  signal, perf: Fix siginfo_t by avoiding u64 on 32-bit architectures
  perf/x86: Allow for 8<num_fixed_counters<16
  perf/x86/rapl: Add support for Intel Alder Lake
  perf/x86/cstate: Add Alder Lake CPU support
  perf/x86/msr: Add Alder Lake CPU support
  perf/x86/intel/uncore: Add Alder Lake support
  perf: Extend PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE
  perf/x86/intel: Add Alder Lake Hybrid support
  perf/x86: Support filter_match callback
  perf/x86/intel: Add attr_update for Hybrid PMUs
  perf/x86: Add structures for the attributes of Hybrid PMUs
  perf/x86: Register hybrid PMUs
  perf/x86: Factor out x86_pmu_show_pmu_cap
  perf/x86: Remove temporary pmu assignment in event_init
  perf/x86/intel: Factor out intel_pmu_check_extra_regs
  perf/x86/intel: Factor out intel_pmu_check_event_constraints
  perf/x86/intel: Factor out intel_pmu_check_num_counters
  perf/x86: Hybrid PMU support for extra_regs
  perf/x86: Hybrid PMU support for event constraints
  ...
2021-04-28 13:03:44 -07:00
Linus Torvalds
eb6bbacc46 Livepatching changes for 5.13
-----BEGIN PGP SIGNATURE-----
 
 iQIzBAABCAAdFiEESH4wyp42V4tXvYsjUqAMR0iAlPIFAmCIF5EACgkQUqAMR0iA
 lPIABA/+MstVI15QFRD50xo/TyGUP3r7NZmU7BTbhzshSW2XkXFiWNn73VeULhZ8
 CDXf8bKuD2tIQTq30+RMRqmSUSN00mXepupA1eVeyKoUYqXzNsEU6oQBRQ3wKYQY
 HrvbcJtIMNC10G7TUIgltiqKsi5538YIfWn5EBN9wvxyHvnJQ/RzNS1OBIaDx+vV
 04E/65P+gcrNMBRXB03/Vl2KBfJQKb4Hj78Yo9puq6kJmV3uHmHgv2adYGT/veG/
 2o+cigfJS1uLg6vCiJC9bBkQgNJUj/3p+6EaVBFfgpZ1ddKW9AVEQMv2PDvaWCuR
 BKwuawobHl1eHgCPS+dofZMFZ0LT+z0pnf8jpduLmbcKFbHYaWLwmPjwFwSQNJ6e
 zqM91pnwRUkSVXmboxubcNHbioRFXhvIiswxHHbrzS4BBs3mXfSEnMRlbB75iKuJ
 cazVRP6u+ukg7XZhtsL2/8UYXOJ4bbIF7R9B/DM5o4zJD2gs9fRCkfDrp2n0Twtu
 x7NffZAAmlqBQ+7c9d/eEkZmzpkX76gRwUC/IvwJRIs+jOHfEehe+tPuqDlWN19b
 vM0a+kup0n8T/ZCfLeK8PLayjm8/hnNg2CK970zlovEKAdCIMovJHUJjnXboSx/n
 +4R/DH3LUG3TJo+rMKLCOZt9/ph2YC1ySTmOXv9GkE0VlsCn95c=
 =ZMd+
 -----END PGP SIGNATURE-----

Merge tag 'livepatching-for-5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching

Pull livepatching update from Petr Mladek:

 - Use TIF_NOTIFY_SIGNAL infrastructure instead of the fake signal

* tag 'livepatching-for-5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching:
  livepatch: Replace the fake signal sending with TIF_NOTIFY_SIGNAL infrastructure
2021-04-27 18:14:38 -07:00
Marco Elver
ed8e50800b signal, perf: Add missing TRAP_PERF case in siginfo_layout()
Add the missing TRAP_PERF case in siginfo_layout() for interpreting the
layout correctly as SIL_PERF_EVENT instead of just SIL_FAULT. This
ensures the si_perf field is copied and not just the si_addr field.

This was caught and tested by running the perf_events/sigtrap_threads
kselftest as a 32-bit binary with a 64-bit kernel.

Fixes: fb6cc127e0 ("signal: Introduce TRAP_PERF si_code and si_perf to siginfo")
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210422191823.79012-2-elver@google.com
2021-04-23 09:03:16 +02:00
Ingo Molnar
d0d252b8ca Linux 5.12-rc8
-----BEGIN PGP SIGNATURE-----
 
 iQFSBAABCAA8FiEEq68RxlopcLEwq+PEeb4+QwBBGIYFAmB8qHweHHRvcnZhbGRz
 QGxpbnV4LWZvdW5kYXRpb24ub3JnAAoJEHm+PkMAQRiGEXIIAILUbsTJsNsvZIkZ
 uQ6SY6gnsPFkRiSRjY0YsZLUnqjTuiiHeTz4gzkonddwdnAp/9g6OIHIEBaeTqBh
 sTUMU/61Fgtrt/IvkA1yJ3rlawqgwdMe2VdimB+EFhufcSKq+5vpd3MVP4IuGx4E
 J3psoTU4gVltFs5t+1QjvI3XmByN0Qm8FMRXR7iL+zov1QTmGwR3G6Rn4AymG+QT
 pdruKboyZPfsrFGSVx7wd3HpFyQcrclEX9rKmBNZqets9d9JGWnqnEN4vQKmwO86
 4MV29ucdMXH0AMB3kzGdVp0Ji2Ykt5W0K+MUWbFLtcSxnpu1OyBKGsEAMlRbD7ik
 gm0bMSw=
 =qHI0
 -----END PGP SIGNATURE-----

Merge tag 'v5.12-rc8' into sched/core, to pick up fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2021-04-20 10:13:58 +02:00
Marco Elver
fb6cc127e0 signal: Introduce TRAP_PERF si_code and si_perf to siginfo
Introduces the TRAP_PERF si_code, and associated siginfo_t field
si_perf. These will be used by the perf event subsystem to send signals
(if requested) to the task where an event occurred.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> # m68k
Acked-by: Arnd Bergmann <arnd@arndb.de> # asm-generic
Link: https://lkml.kernel.org/r/20210408103605.1676875-6-elver@google.com
2021-04-16 16:32:41 +02:00
Thomas Gleixner
4bad58ebc8 signal: Allow tasks to cache one sigqueue struct
The idea for this originates from the real time tree to make signal
delivery for realtime applications more efficient. In quite some of these
application scenarios a control tasks signals workers to start their
computations. There is usually only one signal per worker on flight.  This
works nicely as long as the kmem cache allocations do not hit the slow path
and cause latencies.

To cure this an optimistic caching was introduced (limited to RT tasks)
which allows a task to cache a single sigqueue in a pointer in task_struct
instead of handing it back to the kmem cache after consuming a signal. When
the next signal is sent to the task then the cached sigqueue is used
instead of allocating a new one. This solved the problem for this set of
application scenarios nicely.

The task cache is not preallocated so the first signal sent to a task goes
always to the cache allocator. The cached sigqueue stays around until the
task exits and is freed when task::sighand is dropped.

After posting this solution for mainline the discussion came up whether
this would be useful in general and should not be limited to realtime
tasks: https://lore.kernel.org/r/m11rcu7nbr.fsf@fess.ebiederm.org

One concern leading to the original limitation was to avoid a large amount
of pointlessly cached sigqueues in alive tasks. The other concern was
vs. RLIMIT_SIGPENDING as these cached sigqueues are not accounted for.

The accounting problem is real, but on the other hand slightly academic.
After gathering some statistics it turned out that after boot of a regular
distro install there are less than 10 sigqueues cached in ~1500 tasks.

In case of a 'mass fork and fire signal to child' scenario the extra 80
bytes of memory per task are well in the noise of the overall memory
consumption of the fork bomb.

If this should be limited then this would need an extra counter in struct
user, more atomic instructions and a seperate rlimit. Yet another tunable
which is mostly unused.

The caching is actually used. After boot and a full kernel compile on a
64CPU machine with make -j128 the number of 'allocations' looks like this:

  From slab:	   23996
  From task cache: 52223

I.e. it reduces the number of slab cache operations by ~68%.

A typical pattern there is:

<...>-58490 __sigqueue_alloc:  for 58488 from slab ffff8881132df460
<...>-58488 __sigqueue_free:   cache ffff8881132df460
<...>-58488 __sigqueue_alloc:  for 1149 from cache ffff8881103dc550
  bash-1149 exit_task_sighand: free ffff8881132df460
  bash-1149 __sigqueue_free:   cache ffff8881103dc550

The interesting sequence is that the exiting task 58488 grabs the sigqueue
from bash's task cache to signal exit and bash sticks it back into it's own
cache. Lather, rinse and repeat.

The caching is probably not noticable for the general use case, but the
benefit for latency sensitive applications is clear. While kmem caches are
usually just serving from the fast path the slab merging (default) can
depending on the usage pattern of the merged slabs cause occasional slow
path allocations.

The time spared per cached entry is a few micro seconds per signal which is
not relevant for e.g. a kernel build, but for signal heavy workloads it's
measurable.

As there is no real downside of this caching mechanism making it
unconditionally available is preferred over more conditional code or new
magic tunables.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lkml.kernel.org/r/87sg4lbmxo.fsf@nanos.tec.linutronix.de
2021-04-14 18:04:08 +02:00
Thomas Gleixner
69995ebbb9 signal: Hand SIGQUEUE_PREALLOC flag to __sigqueue_alloc()
There is no point in having the conditional at the callsite.

Just hand in the allocation mode flag to __sigqueue_alloc() and use it to
initialize sigqueue::flags.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210322092258.898677147@linutronix.de
2021-04-14 18:04:08 +02:00
Miroslav Benes
8df1947c71 livepatch: Replace the fake signal sending with TIF_NOTIFY_SIGNAL infrastructure
Livepatch sends a fake signal to all remaining blocking tasks of a
running transition after a set period of time. It uses TIF_SIGPENDING
flag for the purpose. Commit 12db8b6900 ("entry: Add support for
TIF_NOTIFY_SIGNAL") added a generic infrastructure to achieve the same.
Replace our bespoke solution with the generic one.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2021-03-30 09:40:21 +02:00
Jens Axboe
1e4cf0d3d0 Revert "signal: don't allow STOP on PF_IO_WORKER threads"
This reverts commit 4db4b1a0d1.

The IO threads allow and handle SIGSTOP now, so don't special case them
anymore in task_set_jobctl_pending().

Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-03-27 14:09:11 -06:00
Jens Axboe
e8b33b8cfa Revert "kernel: treat PF_IO_WORKER like PF_KTHREAD for ptrace/signals"
This reverts commit 6fb8f43ced.

The IO threads do allow signals now, including SIGSTOP, and we can allow
ptrace attach. Attaching won't reveal anything interesting for the IO
threads, but it will allow eg gdb to attach to a task with io_urings
and IO threads without complaining. And once attached, it will allow
the usual introspection into regular threads.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-03-27 14:09:10 -06:00
Jens Axboe
5a842a7448 Revert "signal: don't allow sending any signals to PF_IO_WORKER threads"
This reverts commit 5be28c8f85.

IO threads now take signals just fine, so there's no reason to limit them
specifically. Revert the change that prevented that from happening.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-03-27 14:09:10 -06:00
Jens Axboe
10442994ba kernel: don't call do_exit() for PF_IO_WORKER threads
Right now we're never calling get_signal() from PF_IO_WORKER threads, but
in preparation for doing so, don't handle a fatal signal for them. The
workers have state they need to cleanup when exiting, so just return
instead of calling do_exit() on their behalf. The threads themselves will
detect a fatal signal and do proper shutdown.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-03-26 16:10:14 -06:00
Eric W. Biederman
4db4b1a0d1 signal: don't allow STOP on PF_IO_WORKER threads
Just like we don't allow normal signals to IO threads, don't deliver a
STOP to a task that has PF_IO_WORKER set. The IO threads don't take
signals in general, and have no means of flushing out a stop either.

Longer term, we may want to look into allowing stop of these threads,
as it relates to eg process freezing. For now, this prevents a spin
issue if a SIGSTOP is delivered to the parent task.

Reported-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-03-21 09:41:07 -06:00
Jens Axboe
5be28c8f85 signal: don't allow sending any signals to PF_IO_WORKER threads
They don't take signals individually, and even if they share signals with
the parent task, don't allow them to be delivered through the worker
thread. Linux does allow this kind of behavior for regular threads, but
it's really a compatability thing that we need not care about for the IO
threads.

Reported-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-03-21 09:39:32 -06:00
Jens Axboe
6fb8f43ced kernel: treat PF_IO_WORKER like PF_KTHREAD for ptrace/signals
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-02-21 17:25:22 -07:00
Linus Torvalds
c509ce2378 for-linus-2021-01-24
-----BEGIN PGP SIGNATURE-----
 
 iHUEABYKAB0WIQRAhzRXHqcMeLMyaSiRxhvAZXjcogUCYA1opwAKCRCRxhvAZXjc
 osnpAP4wjExvtwgh1eA7IgBPtAFzL1EPK2lrv7WM6yuMJNh23wEAxU+quoNrBT7U
 R5UQvmXi2SwxjeGXR/BTLq/HU9rSJA4=
 =6YJX
 -----END PGP SIGNATURE-----

Merge tag 'for-linus-2021-01-24' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull misc fixes from Christian Brauner:

 - Jann reported sparse complaints because of a missing __user
   annotation in a helper we added way back when we added
   pidfd_send_signal() to avoid compat syscall handling. Fix it.

 - Yanfei replaces a reference in a comment to the _do_fork() helper I
   removed a while ago with a reference to the new kernel_clone()
   replacement

 - Alexander Guril added a simple coding style fix

* tag 'for-linus-2021-01-24' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  kthread: remove comments about old _do_fork() helper
  Kernel: fork.c: Fix coding style: Do not use {} around single-line statements
  signal: Add missing __user annotation to copy_siginfo_from_user_any
2021-01-24 09:35:28 -08:00
Jann Horn
adc5d87572
signal: Add missing __user annotation to copy_siginfo_from_user_any
copy_siginfo_from_user_any() takes a userspace pointer as second
argument; annotate the parameter type accordingly.

Signed-off-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20201207000252.138564-1-jannh@google.com
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-11 12:55:00 +01:00
Jens Axboe
35d0b389f3 task_work: unconditionally run task_work from get_signal()
Song reported a boot regression in a kvm image with 5.11-rc, and bisected
it down to the below patch. Debugging this issue, turns out that the boot
stalled when a task is waiting on a pipe being released. As we no longer
run task_work from get_signal() unless it's queued with TWA_SIGNAL, the
task goes idle without running the task_work. This prevents ->release()
from being called on the pipe, which another boot task is waiting on.

For now, re-instate the unconditional task_work run from get_signal().
For 5.12, we'll collapse TWA_RESUME and TWA_SIGNAL, as it no longer
makes sense to have a distinction between the two. This will turn
task_work notification into a simple boolean, whether to notify or not.

Fixes: 98b89b649f ("signal: kill JOBCTL_TASK_WORK")
Reported-by: Song Liu <songliubraving@fb.com>
Tested-by: John Stultz <john.stultz@linaro.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM/Clang version 11.0.1
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-01-08 09:14:21 -07:00
Linus Torvalds
005b2a9dc8 tif-task_work.arch-2020-12-14
-----BEGIN PGP SIGNATURE-----
 
 iQJEBAABCAAuFiEEwPw5LcreJtl1+l5K99NY+ylx4KYFAl/YJxsQHGF4Ym9lQGtl
 cm5lbC5kawAKCRD301j7KXHgpjpyEACBdW+YjenjTbkUPeEXzQgkBkTZUYw3g007
 DPcUT1g8PQZXYXlQvBKCvGhhIr7/KVcjepKoowiNQfBNGcIPJTVopW58nzpqAfTQ
 goI2WYGn5EKFFKBPvtH04cJD/Wo8muXdxynKtqyZbnGGgZjQxPrE259b8dpHjBSR
 6L7HHkk0D1oU/5b6h6Ocpg9mc/0iIUCZylySAYY3eGO0JaVPJaXgZSJZYgHxCHll
 Lb+/y/fXdtm/0PmQ3ko0ev54g3yEWqZIX0NsZW1asrButIy+KLzQ2Mz1xFLFDMag
 prtIfwb8tzgc4dFPY090C/azjCh5CPpxqYS6FkRwS0p86n6OhkyXrqfily5Hs4/B
 NC7CBPBSH/j+NKUK7CYZcpTzTpxPjUr9p0anUdlvMJz8FhTb/3YEEZ1UTeWOeHmk
 Yo5SxnFghLeZZeZ1ok6rdymnVa7WEX12SCLGQX31BB2mld0tNbKb4b+FsBF6OUMk
 IUaX6OjwDFVRaysC88BQ4hjcIP1HxsViG4/VZDX15gjAAH2Pvb+7tev+lcDcOhjz
 TCD4GNFspTFzRhh9nT7oxQ679qCh9G9zHbzuIRewnrS6iqvo5SJQB3dR2yrWZRRH
 ySkQFiHpYOlnLJYv0jg9COlGwo2FUdcvKhCvkjQKKBz48rzW/IC0LwKdRQWZDFk3
 FKGzP/NBig==
 =cadT
 -----END PGP SIGNATURE-----

Merge tag 'tif-task_work.arch-2020-12-14' of git://git.kernel.dk/linux-block

Pull TIF_NOTIFY_SIGNAL updates from Jens Axboe:
 "This sits on top of of the core entry/exit and x86 entry branch from
  the tip tree, which contains the generic and x86 parts of this work.

  Here we convert the rest of the archs to support TIF_NOTIFY_SIGNAL.

  With that done, we can get rid of JOBCTL_TASK_WORK from task_work and
  signal.c, and also remove a deadlock work-around in io_uring around
  knowing that signal based task_work waking is invoked with the sighand
  wait queue head lock.

  The motivation for this work is to decouple signal notify based
  task_work, of which io_uring is a heavy user of, from sighand. The
  sighand lock becomes a huge contention point, particularly for
  threaded workloads where it's shared between threads. Even outside of
  threaded applications it's slower than it needs to be.

  Roman Gershman <romger@amazon.com> reported that his networked
  workload dropped from 1.6M QPS at 80% CPU to 1.0M QPS at 100% CPU
  after io_uring was changed to use TIF_NOTIFY_SIGNAL. The time was all
  spent hammering on the sighand lock, showing 57% of the CPU time there
  [1].

  There are further cleanups possible on top of this. One example is
  TIF_PATCH_PENDING, where a patch already exists to use
  TIF_NOTIFY_SIGNAL instead. Hopefully this will also lead to more
  consolidation, but the work stands on its own as well"

[1] https://github.com/axboe/liburing/issues/215

* tag 'tif-task_work.arch-2020-12-14' of git://git.kernel.dk/linux-block: (28 commits)
  io_uring: remove 'twa_signal_ok' deadlock work-around
  kernel: remove checking for TIF_NOTIFY_SIGNAL
  signal: kill JOBCTL_TASK_WORK
  io_uring: JOBCTL_TASK_WORK is no longer used by task_work
  task_work: remove legacy TWA_SIGNAL path
  sparc: add support for TIF_NOTIFY_SIGNAL
  riscv: add support for TIF_NOTIFY_SIGNAL
  nds32: add support for TIF_NOTIFY_SIGNAL
  ia64: add support for TIF_NOTIFY_SIGNAL
  h8300: add support for TIF_NOTIFY_SIGNAL
  c6x: add support for TIF_NOTIFY_SIGNAL
  alpha: add support for TIF_NOTIFY_SIGNAL
  xtensa: add support for TIF_NOTIFY_SIGNAL
  arm: add support for TIF_NOTIFY_SIGNAL
  microblaze: add support for TIF_NOTIFY_SIGNAL
  hexagon: add support for TIF_NOTIFY_SIGNAL
  csky: add support for TIF_NOTIFY_SIGNAL
  openrisc: add support for TIF_NOTIFY_SIGNAL
  sh: add support for TIF_NOTIFY_SIGNAL
  um: add support for TIF_NOTIFY_SIGNAL
  ...
2020-12-16 12:33:35 -08:00
Linus Torvalds
1ac0884d54 A set of updates for entry/exit handling:
- More generalization of entry/exit functionality
 
  - The consolidation work to reclaim TIF flags on x86 and also for non-x86
    specific TIF flags which are solely relevant for syscall related work
    and have been moved into their own storage space. The x86 specific part
    had to be merged in to avoid a major conflict.
 
  - The TIF_NOTIFY_SIGNAL work which replaces the inefficient signal
    delivery mode of task work and results in an impressive performance
    improvement for io_uring. The non-x86 consolidation of this is going to
    come seperate via Jens.
 
  - The selective syscall redirection facility which provides a clean and
    efficient way to support the non-Linux syscalls of WINE by catching them
    at syscall entry and redirecting them to the user space emulation. This
    can be utilized for other purposes as well and has been designed
    carefully to avoid overhead for the regular fastpath. This includes the
    core changes and the x86 support code.
 
  - Simplification of the context tracking entry/exit handling for the users
    of the generic entry code which guarantee the proper ordering and
    protection.
 
  - Preparatory changes to make the generic entry code accomodate S390
    specific requirements which are mostly related to their syscall restart
    mechanism.
 -----BEGIN PGP SIGNATURE-----
 
 iQJHBAABCgAxFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAl/XoPoTHHRnbHhAbGlu
 dXRyb25peC5kZQAKCRCmGPVMDXSYoe0tD/4jSKHIogVM9kVpiYfwjDGS1NluaBXn
 71ZoASbX9GZebyGandMyF2QP1iJ24ZO0RztBwHEVH6fyomKB2iFNedssCpO9yfWV
 3eFRpOvMpbszY2W2bd0QG3GrqaTttjVfB4ahkGLzqeSbchdob6hZpNDYtBZnujA6
 GSnrrurfJkCGoQny+yJQYdQJXQU+BIX90B2a2Q+jW123Luy/iHXC1f/krZSA1m14
 fC9xYLSUjPphTzh2ZOW+C3DgdjOL5PfAm/6F+DArt4GtLgrEGD7R74aLSFhvetky
 dn5QtG+yAsz1i0cc5Wu/JBcT9tOkY92rPYSyLI9bYQUSQ/bMyuprz6oYKj3dubsu
 ZSsKPdkNFPIniL4fLdCMWZcIXX5xgnrxKjdgXZXW3gtrcxSns8w8uED3Sh7dgE08
 pgIeq67E5g/OB8kJXH1VxdewmeQb9cOmnzzHwNO7TrrGbBKjDTYHNdYOKf1dUTTK
 ZX1UjLfGwxTkMYAbQD1k0JGZ2OLRshzSaH5BW/ZKa3bvJW6yYOq+/YT8B8hbJ8U3
 vThlO75/55IJxS5r5Y3vZd/IHdsYbPuETD+TA8tNYtPqNZasW8nnk4TYctWqzDuO
 /Ka1wvWYid3c6ySznQn4zSyRjr968AfHeZ9YTUMhWufy5waXVmdBMG41u3IKfsVt
 osyzNc4EK19/Mg==
 =hsjV
 -----END PGP SIGNATURE-----

Merge tag 'core-entry-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull core entry/exit updates from Thomas Gleixner:
 "A set of updates for entry/exit handling:

   - More generalization of entry/exit functionality

   - The consolidation work to reclaim TIF flags on x86 and also for
     non-x86 specific TIF flags which are solely relevant for syscall
     related work and have been moved into their own storage space. The
     x86 specific part had to be merged in to avoid a major conflict.

   - The TIF_NOTIFY_SIGNAL work which replaces the inefficient signal
     delivery mode of task work and results in an impressive performance
     improvement for io_uring. The non-x86 consolidation of this is
     going to come seperate via Jens.

   - The selective syscall redirection facility which provides a clean
     and efficient way to support the non-Linux syscalls of WINE by
     catching them at syscall entry and redirecting them to the user
     space emulation. This can be utilized for other purposes as well
     and has been designed carefully to avoid overhead for the regular
     fastpath. This includes the core changes and the x86 support code.

   - Simplification of the context tracking entry/exit handling for the
     users of the generic entry code which guarantee the proper ordering
     and protection.

   - Preparatory changes to make the generic entry code accomodate S390
     specific requirements which are mostly related to their syscall
     restart mechanism"

* tag 'core-entry-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
  entry: Add syscall_exit_to_user_mode_work()
  entry: Add exit_to_user_mode() wrapper
  entry_Add_enter_from_user_mode_wrapper
  entry: Rename exit_to_user_mode()
  entry: Rename enter_from_user_mode()
  docs: Document Syscall User Dispatch
  selftests: Add benchmark for syscall user dispatch
  selftests: Add kselftest for syscall user dispatch
  entry: Support Syscall User Dispatch on common syscall entry
  kernel: Implement selective syscall userspace redirection
  signal: Expose SYS_USER_DISPATCH si_code type
  x86: vdso: Expose sigreturn address on vdso to the kernel
  MAINTAINERS: Add entry for common entry code
  entry: Fix boot for !CONFIG_GENERIC_ENTRY
  x86: Support HAVE_CONTEXT_TRACKING_OFFSTACK
  context_tracking: Only define schedule_user() on !HAVE_CONTEXT_TRACKING_OFFSTACK archs
  sched: Detect call to schedule from critical entry code
  context_tracking: Don't implement exception_enter/exit() on CONFIG_HAVE_CONTEXT_TRACKING_OFFSTACK
  context_tracking: Introduce HAVE_CONTEXT_TRACKING_OFFSTACK
  x86: Reclaim unused x86 TI flags
  ...
2020-12-14 17:13:53 -08:00
Jens Axboe
e296dc4996 kernel: remove checking for TIF_NOTIFY_SIGNAL
It's available everywhere now, no need to check or add dummy defines.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-12-12 09:17:38 -07:00
Jens Axboe
98b89b649f signal: kill JOBCTL_TASK_WORK
It's no longer used, get rid of it.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-12-12 09:17:38 -07:00
Peter Collingbourne
6ac05e832a signal: define the SA_EXPOSE_TAGBITS bit in sa_flags
Architectures that support address tagging, such as arm64, may want to
expose fault address tag bits to the signal handler to help diagnose
memory errors. However, these bits have not been previously set,
and their presence may confuse unaware user applications. Therefore,
introduce a SA_EXPOSE_TAGBITS flag bit in sa_flags that a signal
handler may use to explicitly request that the bits are set.

The generic signal handler APIs expect to receive tagged addresses.
Architectures may specify how to untag addresses in the case where
SA_EXPOSE_TAGBITS is clear by defining the arch_untagged_si_addr
function.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Link: https://linux-review.googlesource.com/id/I16dd0ed2081f091fce97be0190cb8caa874c26cb
Link: https://lkml.kernel.org/r/13cf24d00ebdd8e1f55caf1821c7c29d54100191.1605904350.git.pcc@google.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2020-11-23 10:31:06 -06:00
Peter Collingbourne
a54f0dfda7 signal: define the SA_UNSUPPORTED bit in sa_flags
Define a sa_flags bit, SA_UNSUPPORTED, which will never be supported
in the uapi. The purpose of this flag bit is to allow userspace to
distinguish an old kernel that does not clear unknown sa_flags bits
from a kernel that supports every flag bit.

In other words, if userspace does something like:

  act.sa_flags |= SA_UNSUPPORTED;
  sigaction(SIGSEGV, &act, 0);
  sigaction(SIGSEGV, 0, &oldact);

and finds that SA_UNSUPPORTED remains set in oldact.sa_flags, it means
that the kernel cannot be trusted to have cleared unknown flag bits
from sa_flags, so no assumptions about flag bit support can be made.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Link: https://linux-review.googlesource.com/id/Ic2501ad150a3a79c1cf27fb8c99be342e9dffbcb
Link: https://lkml.kernel.org/r/bda7ddff8895a9bc4ffc5f3cf3d4d37a32118077.1605582887.git.pcc@google.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2020-11-23 10:31:06 -06:00
Peter Collingbourne
23acdc76f1 signal: clear non-uapi flag bits when passing/returning sa_flags
Previously we were not clearing non-uapi flag bits in
sigaction.sa_flags when storing the userspace-provided sa_flags or
when returning them via oldact. Start doing so.

This allows userspace to detect missing support for flag bits and
allows the kernel to use non-uapi bits internally, as we are already
doing in arch/x86 for two flag bits. Now that this change is in
place, we no longer need the code in arch/x86 that was hiding these
bits from userspace, so remove it.

This is technically a userspace-visible behavior change for sigaction, as
the unknown bits returned via oldact.sa_flags are no longer set. However,
we are free to define the behavior for unknown bits exactly because
their behavior is currently undefined, so for now we can define the
meaning of each of them to be "clear the bit in oldact.sa_flags unless
the bit becomes known in the future". Furthermore, this behavior is
consistent with OpenBSD [1], illumos [2] and XNU [3] (FreeBSD [4] and
NetBSD [5] fail the syscall if unknown bits are set). So there is some
precedent for this behavior in other kernels, and in particular in XNU,
which is probably the most popular kernel among those that I looked at,
which means that this change is less likely to be a compatibility issue.

Link: [1] f634a6a4b5/sys/kern/kern_sig.c (L278)
Link: [2] 76f19f5fdc/usr/src/uts/common/syscall/sigaction.c (L86)
Link: [3] a449c6a3b8/bsd/kern/kern_sig.c (L480)
Link: [4] eded70c370/sys/kern/kern_sig.c (L699)
Link: [5] 3365779bec/sys/kern/sys_sig.c (L473)
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Link: https://linux-review.googlesource.com/id/I35aab6f5be932505d90f3b3450c083b4db1eca86
Link: https://lkml.kernel.org/r/878dbcb5f47bc9b11881c81f745c0bef5c23f97f.1605235762.git.pcc@google.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2020-11-23 10:31:05 -06:00
Jens Axboe
29701d69b9 Core changes to support TASK_NOTIFY_SIGNAL
-----BEGIN PGP SIGNATURE-----
 
 iQJHBAABCgAxFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAl+pR0MTHHRnbHhAbGlu
 dXRyb25peC5kZQAKCRCmGPVMDXSYoSWpD/93kyOy0L7NkIELgM6/OHipjsLC6K12
 jMXifA5DfmIIm31sLLzLk08YPz4TOJU+lZKn1DGdqYLioMvvsJe3uZP/WQVyV81z
 QnqdwOpdJVxq7JIjQW04eaVDWjXmxFGmbjKq/tbGexph0hckOtUq/7JOEukzgbLX
 q5iZqYgFouU/G5HIW5Um21WiEVmzzjTFMp13zbqo3rMrG9vXIb5JQxm+TkBbx2P7
 u2kS8R3OFScQcH6UyhaFBBmNFyUHtfbMKPESnhVSXUggQ0aVhNi6pjylE2ZaEIB+
 d7C/yNGNwlC7rGPlh49W5gH5rogrX2Ft2YVrHf645q3Sj/GhbXZ1NqT4f1DJt5uM
 tKjKFxJv6g1dT7ejlUQmseAtLI4ue2wj3C0qtPeHOnUlPHlaDlkTLE2oaCh97Mgn
 mDpAZVnMOcLMRuBFt1J+fnoYcBHwXlfT1rAj//U6m6Pi5BbwIVwTsok5Vsysms4L
 Tyx31zXee3XTp8FEWRL9gqH0b5zXxEUuHxZkqu4vdQDf+wkTi08Q4FpGnhaxGBrY
 CHTwm42hmOK80hdQ6Vv4O38LkQcaEpTztVRexP7a89Q3zxmGlL5BsWGqIIoai0Fg
 8UWmHvauG3kqAif6giWv3QNQ5v0rWksHNxU1yK0tRT6s03no3Kz1eoHHLar8+hoU
 8+/AY23fcJookg==
 =SPWC
 -----END PGP SIGNATURE-----

Merge tag 'core-entry-notify-signal' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into tif-task_work.arch

Core changes to support TASK_NOTIFY_SIGNAL

* tag 'core-entry-notify-signal' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  task_work: Use TIF_NOTIFY_SIGNAL if available
  entry: Add support for TIF_NOTIFY_SIGNAL
  signal: Add task_sigpending() helper
2020-11-09 07:19:32 -07:00
Thomas Gleixner
01be83eea0 Merge branch 'core/urgent' into core/entry
Pick up the entry fix before further modifications.
2020-11-04 18:14:52 +01:00
Oleg Nesterov
7b3c36fc4c ptrace: fix task_join_group_stop() for the case when current is traced
This testcase

	#include <stdio.h>
	#include <unistd.h>
	#include <signal.h>
	#include <sys/ptrace.h>
	#include <sys/wait.h>
	#include <pthread.h>
	#include <assert.h>

	void *tf(void *arg)
	{
		return NULL;
	}

	int main(void)
	{
		int pid = fork();
		if (!pid) {
			kill(getpid(), SIGSTOP);

			pthread_t th;
			pthread_create(&th, NULL, tf, NULL);

			return 0;
		}

		waitpid(pid, NULL, WSTOPPED);

		ptrace(PTRACE_SEIZE, pid, 0, PTRACE_O_TRACECLONE);
		waitpid(pid, NULL, 0);

		ptrace(PTRACE_CONT, pid, 0,0);
		waitpid(pid, NULL, 0);

		int status;
		int thread = waitpid(-1, &status, 0);
		assert(thread > 0 && thread != pid);
		assert(status == 0x80137f);

		return 0;
	}

fails and triggers WARN_ON_ONCE(!signr) in do_jobctl_trap().

This is because task_join_group_stop() has 2 problems when current is traced:

	1. We can't rely on the "JOBCTL_STOP_PENDING" check, a stopped tracee
	   can be woken up by debugger and it can clone another thread which
	   should join the group-stop.

	   We need to check group_stop_count || SIGNAL_STOP_STOPPED.

	2. If SIGNAL_STOP_STOPPED is already set, we should not increment
	   sig->group_stop_count and add JOBCTL_STOP_CONSUME. The new thread
	   should stop without another do_notify_parent_cldstop() report.

To clarify, the problem is very old and we should blame
ptrace_init_task().  But now that we have task_join_group_stop() it makes
more sense to fix this helper to avoid the code duplication.

Reported-by: syzbot+3485e3773f7da290eecc@syzkaller.appspotmail.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christian Brauner <christian@brauner.io>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Zhiqiang Liu <liuzhiqiang26@huawei.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201019134237.GA18810@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-11-02 12:14:19 -08:00
Jens Axboe
12db8b6900 entry: Add support for TIF_NOTIFY_SIGNAL
Add TIF_NOTIFY_SIGNAL handling in the generic entry code, which if set,
will return true if signal_pending() is used in a wait loop. That causes an
exit of the loop so that notify_signal tracehooks can be run. If the wait
loop is currently inside a system call, the system call is restarted once
task_work has been processed.

In preparation for only having arch_do_signal() handle syscall restarts if
_TIF_SIGPENDING isn't set, rename it to arch_do_signal_or_restart().  Pass
in a boolean that tells the architecture specific signal handler if it
should attempt to get a signal, or just process a potential syscall
restart.

For !CONFIG_GENERIC_ENTRY archs, add the TIF_NOTIFY_SIGNAL handling to
get_signal(). This is done to minimize the needed architecture changes to
support this feature.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20201026203230.386348-3-axboe@kernel.dk
2020-10-29 09:37:36 +01:00
Jens Axboe
5c251e9dc0 signal: Add task_sigpending() helper
This is in preparation for maintaining signal_pending() as the decider of
whether or not a schedule() loop should be broken, or continue sleeping.
This is different than the core signal use cases, which really need to know
whether an actual signal is pending or not. task_sigpending() returns
non-zero if TIF_SIGPENDING is set.

Only core kernel use cases should care about the distinction between
the two, make sure those use the task_sigpending() helper.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20201026203230.386348-2-axboe@kernel.dk
2020-10-29 09:37:36 +01:00
Gustavo A. R. Silva
df561f6688 treewide: Use fallthrough pseudo-keyword
Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
2020-08-23 17:36:59 -05:00
Jens Axboe
ebf0d100df task_work: only grab task signal lock when needed
If JOBCTL_TASK_WORK is already set on the targeted task, then we need
not go through {lock,unlock}_task_sighand() to set it again and queue
a signal wakeup. This is safe as we're checking it _after_ adding the
new task_work with cmpxchg().

The ordering is as follows:

task_work_add()				get_signal()
--------------------------------------------------------------
STORE(task->task_works, new_work);	STORE(task->jobctl);
mb();					mb();
LOAD(task->jobctl);			LOAD(task->task_works);

This speeds up TWA_SIGNAL handling quite a bit, which is important now
that io_uring is relying on it for all task_work deliveries.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jann Horn <jannh@google.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-13 09:01:38 -06:00
Pavel Machek
7665a47f70
signal: fix typo in dequeue_synchronous_signal()
s/postive/positive/

Signed-off-by: Pavel Machek (CIP) <pavel@denx.de>
Link: https://lore.kernel.org/r/20200724090531.GA14409@amd
[christian.brauner@ubuntu.com: tweak commit message]
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2020-07-26 23:57:52 +02:00
Oleg Nesterov
e91b481623 task_work: teach task_work_add() to do signal_wake_up()
So that the target task will exit the wait_event_interruptible-like
loop and call task_work_run() asap.

The patch turns "bool notify" into 0,TWA_RESUME,TWA_SIGNAL enum, the
new TWA_SIGNAL flag implies signal_wake_up().  However, it needs to
avoid the race with recalc_sigpending(), so the patch also adds the
new JOBCTL_TASK_WORK bit included in JOBCTL_PENDING_MASK.

TODO: once this patch is merged we need to change all current users
of task_work_add(notify = true) to use TWA_RESUME.

Cc: stable@vger.kernel.org # v5.7
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-06-30 12:18:08 -06:00
Linus Torvalds
8b39a57e96 Merge branch 'work.set_fs-exec' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull uaccess/coredump updates from Al Viro:
 "set_fs() removal in coredump-related area - mostly Christoph's
  stuff..."

* 'work.set_fs-exec' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  binfmt_elf_fdpic: remove the set_fs(KERNEL_DS) in elf_fdpic_core_dump
  binfmt_elf: remove the set_fs(KERNEL_DS) in elf_core_dump
  binfmt_elf: remove the set_fs in fill_siginfo_note
  signal: refactor copy_siginfo_to_user32
  powerpc/spufs: simplify spufs core dumping
  powerpc/spufs: stop using access_ok
  powerpc/spufs: fix copy_to_user while atomic
2020-06-01 16:21:46 -07:00