Some thread flags can be set remotely, and so even when IRQs are disabled,
the flags can change under our feet. Generally this is unlikely to cause a
problem in practice, but it is somewhat unsound, and KCSAN will
legitimately warn that there is a data race.
To avoid such issues, a snapshot of the flags has to be taken prior to
using them. Some places already use READ_ONCE() for that, others do not.
Convert them all to the new flag accessor helpers.
The READ_ONCE(ti->flags) .. cmpxchg(ti->flags) loop in
set_nr_if_polling() is left as-is for clarity.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20211129130653.2037928-4-mark.rutland@arm.com
Some thread flags can be set remotely, and so even when IRQs are disabled,
the flags can change under our feet. Generally this is unlikely to cause a
problem in practice, but it is somewhat unsound, and KCSAN will
legitimately warn that there is a data race.
To avoid such issues, a snapshot of the flags has to be taken prior to
using them. Some places already use READ_ONCE() for that, others do not.
Convert them all to the new flag accessor helpers.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20211129130653.2037928-3-mark.rutland@arm.com
This patch adds the kernel-side and API changes for a new helper
function, bpf_loop:
long bpf_loop(u32 nr_loops, void *callback_fn, void *callback_ctx,
u64 flags);
where long (*callback_fn)(u32 index, void *ctx);
bpf_loop invokes the "callback_fn" **nr_loops** times or until the
callback_fn returns 1. The callback_fn can only return 0 or 1, and
this is enforced by the verifier. The callback_fn index is zero-indexed.
A few things to please note:
~ The "u64 flags" parameter is currently unused but is included in
case a future use case for it arises.
~ In the kernel-side implementation of bpf_loop (kernel/bpf/bpf_iter.c),
bpf_callback_t is used as the callback function cast.
~ A program can have nested bpf_loop calls but the program must
still adhere to the verifier constraint of its stack depth (the stack depth
cannot exceed MAX_BPF_STACK))
~ Recursive callback_fns do not pass the verifier, due to the call stack
for these being too deep.
~ The next patch will include the tests and benchmark
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/20211130030622.4131246-2-joannekoong@fb.com
css_alloc() needs the parent css, while cgroup_css() gets current
cgropu's css. So we are getting the wrong css during
cgroup_init_subsys().
Fortunately, cgrp_dfl_root.cgrp's css is not set yet, so the value we
pass to css_alloc() is NULL anyway.
Let's pass NULL directly during init, since we know there is no parent
yet.
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull scheduler fix from Thomas Gleixner:
"A single scheduler fix to ensure that there is no stale KASAN shadow
state left on the idle task's stack when a CPU is brought up after it
was brought down before"
* tag 'sched-urgent-2021-11-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/scs: Reset task stack state in bringup_cpu()
Pull perf fix from Thomas Gleixner:
"A single fix for perf to prevent it from sending SIGTRAP to another
task from a trace point event as it's not possible to deliver a
synchronous signal to a different task from there"
* tag 'perf-urgent-2021-11-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf: Ignore sigtrap for tracepoints destined for other tasks
Pull locking fixes from Thomas Gleixner:
"Two regression fixes for reader writer semaphores:
- Plug a race in the lock handoff which is caused by inconsistency of
the reader and writer path and can lead to corruption of the
underlying counter.
- down_read_trylock() is suboptimal when the lock is contended and
multiple readers trylock concurrently. That's due to the initial
value being read non-atomically which results in at least two
compare exchange loops. Making the initial readout atomic reduces
this significantly. Whith 40 readers by 11% in a benchmark which
enforces contention on mmap_sem"
* tag 'locking-urgent-2021-11-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
locking/rwsem: Optimize down_read_trylock() under highly contended case
locking/rwsem: Make handoff bit handling more consistent
Pull another tracing fix from Steven Rostedt:
"Fix the fix of pid filtering
The setting of the pid filtering flag tested the "trace only this pid"
case twice, and ignored the "trace everything but this pid" case.
The 5.15 kernel does things a little differently due to the new sparse
pid mask introduced in 5.16, and as the bug was discovered running the
5.15 kernel, and the first fix was initially done for that kernel,
that fix handled both cases (only pid and all but pid), but the
forward port to 5.16 created this bug"
* tag 'trace-v5.16-rc2-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing: Test the 'Do not trace this pid' case in create event
When creating a new event (via a module, kprobe, eprobe, etc), the
descriptors that are created must add flags for pid filtering if an
instance has pid filtering enabled, as the flags are used at the time the
event is executed to know if pid filtering should be done or not.
The "Only trace this pid" case was added, but a cut and paste error made
that case checked twice, instead of checking the "Trace all but this pid"
case.
Link: https://lore.kernel.org/all/202111280401.qC0z99JB-lkp@intel.com/
Fixes: 6cb206508b ("tracing: Check pid filtering when creating events")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Pull tracing fixes from Steven Rostedt:
"Two fixes to event pid filtering:
- Make sure newly created events reflect the current state of pid
filtering
- Take pid filtering into account when recording trigger events.
(Also clean up the if statement to be cleaner)"
* tag 'trace-v5.16-rc2-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing: Fix pid filtering when triggers are attached
tracing: Check pid filtering when creating events
If a event is filtered by pid and a trigger that requires processing of
the event to happen is a attached to the event, the discard portion does
not take the pid filtering into account, and the event will then be
recorded when it should not have been.
Cc: stable@vger.kernel.org
Fixes: 3fdaf80f4a ("tracing: Implement event pid filtering")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Pull power management fixes from Rafael Wysocki:
"These address three issues in the intel_pstate driver and fix two
problems related to hibernation.
Specifics:
- Make intel_pstate work correctly on Ice Lake server systems with
out-of-band performance control enabled (Adamos Ttofari).
- Fix EPP handling in intel_pstate during CPU offline and online in
the active mode (Rafael Wysocki).
- Make intel_pstate support ITMT on asymmetric systems with
overclocking enabled (Srinivas Pandruvada).
- Fix hibernation image saving when using the user space interface
based on the snapshot special device file (Evan Green).
- Make the hibernation code release the snapshot block device using
the same mode that was used when acquiring it (Thomas Zeitlhofer)"
* tag 'pm-5.16-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
PM: hibernate: Fix snapshot partial write lengths
PM: hibernate: use correct mode for swsusp_close()
cpufreq: intel_pstate: ITMT support for overclocked system
cpufreq: intel_pstate: Fix active mode offline/online EPP handling
cpufreq: intel_pstate: Add Ice Lake server to out-of-band IDs
When pid filtering is activated in an instance, all of the events trace
files for that instance has the PID_FILTER flag set. This determines
whether or not pid filtering needs to be done on the event, otherwise the
event is executed as normal.
If pid filtering is enabled when an event is created (via a dynamic event
or modules), its flag is not updated to reflect the current state, and the
events are not filtered properly.
Cc: stable@vger.kernel.org
Fixes: 3fdaf80f4a ("tracing: Implement event pid filtering")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
snapshot_write() is inappropriately limiting the amount of data that can
be written in cases where a partial page has already been written. For
example, one would expect to be able to write 1 byte, then 4095 bytes to
the snapshot device, and have both of those complete fully (since now
we're aligned to a page again). But what ends up happening is we write 1
byte, then 4094/4095 bytes complete successfully.
The reason is that simple_write_to_buffer()'s second argument is the
total size of the buffer, not the size of the buffer minus the offset.
Since simple_write_to_buffer() accounts for the offset in its
implementation, snapshot_write() can just pass the full page size
directly down.
Signed-off-by: Evan Green <evgreen@chromium.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Commit 39fbef4b0f ("PM: hibernate: Get block device exclusively in
swsusp_check()") changed the opening mode of the block device to
(FMODE_READ | FMODE_EXCL).
In the corresponding calls to swsusp_close(), the mode is still just
FMODE_READ which triggers the warning in blkdev_flush_mapping() on
resume from hibernate.
So, use the mode (FMODE_READ | FMODE_EXCL) also when closing the
device.
Fixes: 39fbef4b0f ("PM: hibernate: Get block device exclusively in swsusp_check()")
Signed-off-by: Thomas Zeitlhofer <thomas.zeitlhofer+lkml@ze-it.at>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
To hot unplug a CPU, the idle task on that CPU calls a few layers of C
code before finally leaving the kernel. When KASAN is in use, poisoned
shadow is left around for each of the active stack frames, and when
shadow call stacks are in use. When shadow call stacks (SCS) are in use
the task's saved SCS SP is left pointing at an arbitrary point within
the task's shadow call stack.
When a CPU is offlined than onlined back into the kernel, this stale
state can adversely affect execution. Stale KASAN shadow can alias new
stackframes and result in bogus KASAN warnings. A stale SCS SP is
effectively a memory leak, and prevents a portion of the shadow call
stack being used. Across a number of hotplug cycles the idle task's
entire shadow call stack can become unusable.
We previously fixed the KASAN issue in commit:
e1b77c9298 ("sched/kasan: remove stale KASAN poison after hotplug")
... by removing any stale KASAN stack poison immediately prior to
onlining a CPU.
Subsequently in commit:
f1a0a376ca ("sched/core: Initialize the idle task with preemption disabled")
... the refactoring left the KASAN and SCS cleanup in one-time idle
thread initialization code rather than something invoked prior to each
CPU being onlined, breaking both as above.
We fixed SCS (but not KASAN) in commit:
63acd42c0d ("sched/scs: Reset the shadow stack when idle_task_exit")
... but as this runs in the context of the idle task being offlined it's
potentially fragile.
To fix these consistently and more robustly, reset the SCS SP and KASAN
shadow of a CPU's idle task immediately before we online that CPU in
bringup_cpu(). This ensures the idle task always has a consistent state
when it is running, and removes the need to so so when exiting an idle
task.
Whenever any thread is created, dup_task_struct() will give the task a
stack which is free of KASAN shadow, and initialize the task's SCS SP,
so there's no need to specially initialize either for idle thread within
init_idle(), as this was only necessary to handle hotplug cycles.
I've tested this on arm64 with:
* gcc 11.1.0, defconfig +KASAN_INLINE, KASAN_STACK
* clang 12.0.0, defconfig +KASAN_INLINE, KASAN_STACK, SHADOW_CALL_STACK
... offlining and onlining CPUS with:
| while true; do
| for C in /sys/devices/system/cpu/cpu*/online; do
| echo 0 > $C;
| echo 1 > $C;
| done
| done
Fixes: f1a0a376ca ("sched/core: Initialize the idle task with preemption disabled")
Reported-by: Qian Cai <quic_qiancai@quicinc.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Qian Cai <quic_qiancai@quicinc.com>
Link: https://lore.kernel.org/lkml/20211115113310.35693-1-mark.rutland@arm.com/
cpuacct has 2 different ways of accounting and showing user
and system times.
The first one uses cpuacct_account_field() to account times
and cpuacct.stat file to expose them. And this one seems to work ok.
The second one is uses cpuacct_charge() function for accounting and
set of cpuacct.usage* files to show times. Despite some attempts to
fix it in the past it still doesn't work. Sometimes while running KVM
guest the cpuacct_charge() accounts most of the guest time as
system time. This doesn't match with user&system times shown in
cpuacct.stat or proc/<pid>/stat.
Demonstration:
# git clone https://github.com/aryabinin/kvmsample
# make
# mkdir /sys/fs/cgroup/cpuacct/test
# echo $$ > /sys/fs/cgroup/cpuacct/test/tasks
# ./kvmsample &
# for i in {1..5}; do cat /sys/fs/cgroup/cpuacct/test/cpuacct.usage_sys; sleep 1; done
1976535645
2979839428
3979832704
4983603153
5983604157
Use cpustats accounted in cpuacct_account_field() as the source
of user/sys times for cpuacct.usage* files. Make cpuacct_charge()
to account only summary execution time.
Fixes: d740037fac ("sched/cpuacct: Split usage accounting into user_usage and sys_usage")
Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20211115164607.23784-3-arbn@yandex-team.com
syzbot reported that the warning in perf_sigtrap() fires, saying that
the event's task does not match current:
| WARNING: CPU: 0 PID: 9090 at kernel/events/core.c:6446 perf_pending_event+0x40d/0x4b0 kernel/events/core.c:6513
| Modules linked in:
| CPU: 0 PID: 9090 Comm: syz-executor.1 Not tainted 5.15.0-syzkaller #0
| Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
| RIP: 0010:perf_sigtrap kernel/events/core.c:6446 [inline]
| RIP: 0010:perf_pending_event_disable kernel/events/core.c:6470 [inline]
| RIP: 0010:perf_pending_event+0x40d/0x4b0 kernel/events/core.c:6513
| ...
| Call Trace:
| <IRQ>
| irq_work_single+0x106/0x220 kernel/irq_work.c:211
| irq_work_run_list+0x6a/0x90 kernel/irq_work.c:242
| irq_work_run+0x4f/0xd0 kernel/irq_work.c:251
| __sysvec_irq_work+0x95/0x3d0 arch/x86/kernel/irq_work.c:22
| sysvec_irq_work+0x8e/0xc0 arch/x86/kernel/irq_work.c:17
| </IRQ>
| <TASK>
| asm_sysvec_irq_work+0x12/0x20 arch/x86/include/asm/idtentry.h:664
| RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
| RIP: 0010:_raw_spin_unlock_irqrestore+0x38/0x70 kernel/locking/spinlock.c:194
| ...
| coredump_task_exit kernel/exit.c:371 [inline]
| do_exit+0x1865/0x25c0 kernel/exit.c:771
| do_group_exit+0xe7/0x290 kernel/exit.c:929
| get_signal+0x3b0/0x1ce0 kernel/signal.c:2820
| arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
| handle_signal_work kernel/entry/common.c:148 [inline]
| exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
| exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
| __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
| syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
| do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
| entry_SYSCALL_64_after_hwframe+0x44/0xae
On x86 this shouldn't happen, which has arch_irq_work_raise().
The test program sets up a perf event with sigtrap set to fire on the
'sched_wakeup' tracepoint, which fired in ttwu_do_wakeup().
This happened because the 'sched_wakeup' tracepoint also takes a task
argument passed on to perf_tp_event(), which is used to deliver the
event to that other task.
Since we cannot deliver synchronous signals to other tasks, skip an event if
perf_tp_event() is targeted at another task and perf_event_attr::sigtrap is
set, which will avoid ever entering perf_sigtrap() for such events.
Fixes: 97ba62b278 ("perf: Add support for SIGTRAP on perf events")
Reported-by: syzbot+663359e32ce6f1a305ad@syzkaller.appspotmail.com
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YYpoCOBmC/kJWfmI@elver.google.com
We found that a process with 10 thousnads threads has been encountered
a regression problem from Linux-v4.14 to Linux-v5.4. It is a kind of
workload which will concurrently allocate lots of memory in different
threads sometimes. In this case, we will see the down_read_trylock()
with a high hotspot. Therefore, we suppose that rwsem has a regression
at least since Linux-v5.4. In order to easily debug this problem, we
write a simply benchmark to create the similar situation lile the
following.
```c++
#include <sys/mman.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sched.h>
#include <cstdio>
#include <cassert>
#include <thread>
#include <vector>
#include <chrono>
volatile int mutex;
void trigger(int cpu, char* ptr, std::size_t sz)
{
cpu_set_t set;
CPU_ZERO(&set);
CPU_SET(cpu, &set);
assert(pthread_setaffinity_np(pthread_self(), sizeof(set), &set) == 0);
while (mutex);
for (std::size_t i = 0; i < sz; i += 4096) {
*ptr = '\0';
ptr += 4096;
}
}
int main(int argc, char* argv[])
{
std::size_t sz = 100;
if (argc > 1)
sz = atoi(argv[1]);
auto nproc = std::thread::hardware_concurrency();
std::vector<std::thread> thr;
sz <<= 30;
auto* ptr = mmap(nullptr, sz, PROT_READ | PROT_WRITE, MAP_ANON |
MAP_PRIVATE, -1, 0);
assert(ptr != MAP_FAILED);
char* cptr = static_cast<char*>(ptr);
auto run = sz / nproc;
run = (run >> 12) << 12;
mutex = 1;
for (auto i = 0U; i < nproc; ++i) {
thr.emplace_back(std::thread([i, cptr, run]() { trigger(i, cptr, run); }));
cptr += run;
}
rusage usage_start;
getrusage(RUSAGE_SELF, &usage_start);
auto start = std::chrono::system_clock::now();
mutex = 0;
for (auto& t : thr)
t.join();
rusage usage_end;
getrusage(RUSAGE_SELF, &usage_end);
auto end = std::chrono::system_clock::now();
timeval utime;
timeval stime;
timersub(&usage_end.ru_utime, &usage_start.ru_utime, &utime);
timersub(&usage_end.ru_stime, &usage_start.ru_stime, &stime);
printf("usr: %ld.%06ld\n", utime.tv_sec, utime.tv_usec);
printf("sys: %ld.%06ld\n", stime.tv_sec, stime.tv_usec);
printf("real: %lu\n",
std::chrono::duration_cast<std::chrono::milliseconds>(end -
start).count());
return 0;
}
```
The functionality of above program is simply which creates `nproc`
threads and each of them are trying to touch memory (trigger page
fault) on different CPU. Then we will see the similar profile by
`perf top`.
25.55% [kernel] [k] down_read_trylock
14.78% [kernel] [k] handle_mm_fault
13.45% [kernel] [k] up_read
8.61% [kernel] [k] clear_page_erms
3.89% [kernel] [k] __do_page_fault
The highest hot instruction, which accounts for about 92%, in
down_read_trylock() is cmpxchg like the following.
91.89 │ lock cmpxchg %rdx,(%rdi)
Sice the problem is found by migrating from Linux-v4.14 to Linux-v5.4,
so we easily found that the commit ddb20d1d3a ("locking/rwsem: Optimize
down_read_trylock()") caused the regression. The reason is that the
commit assumes the rwsem is not contended at all. But it is not always
true for mmap lock which could be contended with thousands threads.
So most threads almost need to run at least 2 times of "cmpxchg" to
acquire the lock. The overhead of atomic operation is higher than
non-atomic instructions, which caused the regression.
By using the above benchmark, the real executing time on a x86-64 system
before and after the patch were:
Before Patch After Patch
# of Threads real real reduced by
------------ ------ ------ ----------
1 65,373 65,206 ~0.0%
4 15,467 15,378 ~0.5%
40 6,214 5,528 ~11.0%
For the uncontended case, the new down_read_trylock() is the same as
before. For the contended cases, the new down_read_trylock() is faster
than before. The more contended, the more fast.
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20211118094455.9068-1-songmuchun@bytedance.com
There are some inconsistency in the way that the handoff bit is being
handled in readers and writers that lead to a race condition.
Firstly, when a queue head writer set the handoff bit, it will clear
it when the writer is being killed or interrupted on its way out
without acquiring the lock. That is not the case for a queue head
reader. The handoff bit will simply be inherited by the next waiter.
Secondly, in the out_nolock path of rwsem_down_read_slowpath(), both
the waiter and handoff bits are cleared if the wait queue becomes
empty. For rwsem_down_write_slowpath(), however, the handoff bit is
not checked and cleared if the wait queue is empty. This can
potentially make the handoff bit set with empty wait queue.
Worse, the situation in rwsem_down_write_slowpath() relies on wstate,
a variable set outside of the critical section containing the ->count
manipulation, this leads to race condition where RWSEM_FLAG_HANDOFF
can be double subtracted, corrupting ->count.
To make the handoff bit handling more consistent and robust, extract
out handoff bit clearing code into the new rwsem_del_waiter() helper
function. Also, completely eradicate wstate; always evaluate
everything inside the same critical section.
The common function will only use atomic_long_andnot() to clear bits
when the wait queue is empty to avoid possible race condition. If the
first waiter with handoff bit set is killed or interrupted to exit the
slowpath without acquiring the lock, the next waiter will inherit the
handoff bit.
While at it, simplify the trylock for loop in
rwsem_down_write_slowpath() to make it easier to read.
Fixes: 4f23dbc1e6 ("locking/rwsem: Implement lock handoff to prevent lock starvation")
Reported-by: Zhenhua Ma <mazhenhua@xiaomi.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211116012912.723980-1-longman@redhat.com
The security_task_getsecid_subj() LSM hook invites misuse by allowing
callers to specify a task even though the hook is only safe when the
current task is referenced. Fix this by removing the task_struct
argument to the hook, requiring LSM implementations to use the
current task. While we are changing the hook declaration we also
rename the function to security_current_getsecid_subj() in an effort
to reinforce that the hook captures the subjective credentials of the
current task and not an arbitrary task on the system.
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Pull tracing fixes from Steven Rostedt:
- Fix double free in destroy_hist_field
- Harden memset() of trace_iterator structure
- Do not warn in trace printk check when test buffer fills up
* tag 'trace-v5.16-6' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing: Don't use out-of-sync va_list in event printing
tracing: Use memset_startat() to zero struct trace_iterator
tracing/histogram: Fix UAF in destroy_hist_field()
Pull exit-vs-signal handling fixes from Eric Biederman:
"This is a small set of changes where debuggers were no longer able to
intercept synchronous SIGTRAP and SIGSEGV, introduced by the exit
cleanups.
This is essentially the change you suggested with all of i's dotted
and the t's crossed so that ptrace can intercept all of the cases it
has been able to intercept the past, and all of the cases that made it
to exit without giving ptrace a chance still don't give ptrace a
chance"
* 'SA_IMMUTABLE-fixes-for-v5.16-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
signal: Replace force_fatal_sig with force_exit_sig when in doubt
signal: Don't always set SA_IMMUTABLE for forced signals
Recently to prevent issues with SECCOMP_RET_KILL and similar signals
being changed before they are delivered SA_IMMUTABLE was added.
Unfortunately this broke debuggers[1][2] which reasonably expect
to be able to trap synchronous SIGTRAP and SIGSEGV even when
the target process is not configured to handle those signals.
Add force_exit_sig and use it instead of force_fatal_sig where
historically the code has directly called do_exit. This has the
implementation benefits of going through the signal exit path
(including generating core dumps) without the danger of allowing
userspace to ignore or change these signals.
This avoids userspace regressions as older kernels exited with do_exit
which debuggers also can not intercept.
In the future is should be possible to improve the quality of
implementation of the kernel by changing some of these force_exit_sig
calls to force_fatal_sig. That can be done where it matters on
a case-by-case basis with careful analysis.
Reported-by: Kyle Huey <me@kylehuey.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
[1] https://lkml.kernel.org/r/CAP045AoMY4xf8aC_4QU_-j7obuEPYgTcnQQP3Yxk=2X90jtpjw@mail.gmail.com
[2] https://lkml.kernel.org/r/20211117150258.GB5403@xsang-OptiPlex-9020
Fixes: 00b06da29c ("signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed")
Fixes: a3616a3c02 ("signal/m68k: Use force_sigsegv(SIGSEGV) in fpsp040_die")
Fixes: 83a1f27ad7 ("signal/powerpc: On swapcontext failure force SIGSEGV")
Fixes: 9bc508cf07 ("signal/s390: Use force_sigsegv in default_trap_handler")
Fixes: 086ec444f8 ("signal/sparc32: In setup_rt_frame and setup_fram use force_fatal_sig")
Fixes: c317d306d5 ("signal/sparc32: Exit with a fatal signal when try_to_clear_window_buffer fails")
Fixes: 695dd0d634 ("signal/x86: In emulate_vsyscall force a signal instead of calling do_exit")
Fixes: 1fbd60df8a ("signal/vm86_32: Properly send SIGSEGV when the vm86 state cannot be saved.")
Fixes: 941edc5bf1 ("exit/syscall_user_dispatch: Send ordinary signals on failure")
Link: https://lkml.kernel.org/r/871r3dqfv8.fsf_-_@email.froward.int.ebiederm.org
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: Kyle Huey <khuey@kylehuey.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
If trace_seq becomes full, trace_seq_vprintf() no longer consumes
arguments from va_list, making va_list out of sync with format
processing by trace_check_vprintf().
This causes va_arg() in trace_check_vprintf() to return wrong
positional argument, which results into a WARN_ON_ONCE() hit.
ftrace_stress_test from LTP triggers this situation.
Fix it by explicitly avoiding further use if va_list at the point
when it's consistency can no longer be guaranteed.
Link: https://lkml.kernel.org/r/20211118145516.13219-1-nikita.yushchenko@virtuozzo.com
Signed-off-by: Nikita Yushchenko <nikita.yushchenko@virtuozzo.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Pull networking fixes from Jakub Kicinski:
"Including fixes from bpf, mac80211.
Current release - regressions:
- devlink: don't throw an error if flash notification sent before
devlink visible
- page_pool: Revert "page_pool: disable dma mapping support...",
turns out there are active arches who need it
Current release - new code bugs:
- amt: cancel delayed_work synchronously in amt_fini()
Previous releases - regressions:
- xsk: fix crash on double free in buffer pool
- bpf: fix inner map state pruning regression causing program
rejections
- mac80211: drop check for DONT_REORDER in __ieee80211_select_queue,
preventing mis-selecting the best effort queue
- mac80211: do not access the IV when it was stripped
- mac80211: fix radiotap header generation, off-by-one
- nl80211: fix getting radio statistics in survey dump
- e100: fix device suspend/resume
Previous releases - always broken:
- tcp: fix uninitialized access in skb frags array for Rx 0cp
- bpf: fix toctou on read-only map's constant scalar tracking
- bpf: forbid bpf_ktime_get_coarse_ns and bpf_timer_* in tracing
progs
- tipc: only accept encrypted MSG_CRYPTO msgs
- smc: transfer remaining wait queue entries during fallback, fix
missing wake ups
- udp: validate checksum in udp_read_sock() (when sockmap is used)
- sched: act_mirred: drop dst for the direction from egress to
ingress
- virtio_net_hdr_to_skb: count transport header in UFO, prevent
allowing bad skbs into the stack
- nfc: reorder the logic in nfc_{un,}register_device, fix unregister
- ipsec: check return value of ipv6_skip_exthdr
- usb: r8152: add MAC passthrough support for more Lenovo Docks"
* tag 'net-5.16-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (96 commits)
ptp: ocp: Fix a couple NULL vs IS_ERR() checks
net: ethernet: dec: tulip: de4x5: fix possible array overflows in type3_infoblock()
net: tulip: de4x5: fix the problem that the array 'lp->phy[8]' may be out of bound
ipv6: check return value of ipv6_skip_exthdr
e100: fix device suspend/resume
devlink: Don't throw an error if flash notification sent before devlink visible
page_pool: Revert "page_pool: disable dma mapping support..."
ethernet: hisilicon: hns: hns_dsaf_misc: fix a possible array overflow in hns_dsaf_ge_srst_by_port()
octeontx2-af: debugfs: don't corrupt user memory
NFC: add NCI_UNREG flag to eliminate the race
NFC: reorder the logic in nfc_{un,}register_device
NFC: reorganize the functions in nci_request
tipc: check for null after calling kmemdup
i40e: Fix display error code in dmesg
i40e: Fix creation of first queue by omitting it if is not power of two
i40e: Fix warning message and call stack during rmmod i40e driver
i40e: Fix ping is lost after configuring ADq on VF
i40e: Fix changing previously set num_queue_pairs for PFs
i40e: Fix NULL ptr dereference on VSI filter sync
i40e: Fix correct max_pkt_size on VF RX queue
...
Pull printk fixes from Petr Mladek:
- Try to flush backtraces from other CPUs also on the local one. This
was a regression caused by printk_safe buffers removal.
- Remove header dependency warning.
* tag 'printk-for-5.16-fixup' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printk: Remove printk.h inclusion in percpu.h
printk: restore flushing of NMI buffers on remote CPUs after NMI backtraces
Kyle Huey <me@kylehuey.com> writes:
> rr, a userspace record and replay debugger[0], uses the recorded register
> state at PTRACE_EVENT_EXIT to find the point in time at which to cease
> executing the program during replay.
>
> If a SIGKILL races with processing another signal in get_signal, it is
> possible for the kernel to decline to notify the tracer of the original
> signal. But if the original signal had a handler, the kernel proceeds
> with setting up a signal handler frame as if the tracer had chosen to
> deliver the signal unmodified to the tracee. When the kernel goes to
> execute the signal handler that it has now modified the stack and registers
> for, it will discover the pending SIGKILL, and terminate the tracee
> without executing the handler. When PTRACE_EVENT_EXIT is delivered to
> the tracer, however, the effects of handler setup will be visible to
> the tracer.
>
> Because rr (the tracer) was never notified of the signal, it is not aware
> that a signal handler frame was set up and expects the state of the program
> at PTRACE_EVENT_EXIT to be a state that will be reconstructed naturally
> by allowing the program to execute from the last event. When that fails
> to happen during replay, rr will assert and die.
>
> The following patches add an explicit check for a newly pending SIGKILL
> after the ptracer has been notified and the siglock has been reacquired.
> If this happens, we stop processing the current signal and proceed
> immediately to handling the SIGKILL. This makes the state reported at
> PTRACE_EVENT_EXIT the unmodified state of the program, and also avoids the
> work to set up a signal handler frame that will never be used.
>
> [0] https://rr-project.org/
The problem is that while the traced process makes it into ptrace_stop,
the tracee is killed before the tracer manages to wait for the
tracee and discover which signal was about to be delivered.
More generally the problem is that while siglock was dropped a signal
with process wide effect is short cirucit delivered to the entire
process killing it, but the process continues to try and deliver another
signal.
In general it impossible to avoid all cases where work is performed
after the process has been killed. In particular if the process is
killed after get_signal returns the code will simply not know it has
been killed until after delivering the signal frame to userspace.
On the other hand when the code has already discovered the process
has been killed and taken user space visible action that shows
the kernel knows the process has been killed, it is just silly
to then write the signal frame to the user space stack.
Instead of being silly detect the process has been killed
in ptrace_signal and requeue the signal so the code can pretend
it was simply never dequeued for delivery.
To test the process has been killed I use fatal_signal_pending rather
than signal_group_exit to match the test in signal_pending_state which
is used in schedule which is where ptrace_stop detects the process has
been killed.
Requeuing the signal so the code can pretend it was simply never
dequeued improves the user space visible behavior that has been
present since ebf5ebe31d2c ("[PATCH] signal-fixes-2.5.59-A4").
Kyle Huey verified that this change in behavior and makes rr happy.
Reported-by: Kyle Huey <khuey@kylehuey.com>
Reported-by: Marko Mäkelä <marko.makela@mariadb.com>
History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.gi
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/87tugcd5p2.fsf_-_@email.froward.int.ebiederm.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
In the event that a tracer changes which signal needs to be delivered
and that signal is currently blocked then the signal needs to be
requeued for later delivery.
With the advent of CLONE_THREAD the kernel has 2 signal queues per
task. The per process queue and the per task queue. Update the code
so that if the signal is removed from the per process queue it is
requeued on the per process queue. This is necessary to make it
appear the signal was never dequeued.
The rr debugger reasonably believes that the state of the process from
the last ptrace_stop it observed until PTRACE_EVENT_EXIT can be recreated
by simply letting a process run. If a SIGKILL interrupts a ptrace_stop
this is not true today.
So return signals to their original queue in ptrace_signal so that
signals that are not delivered appear like they were never dequeued.
Fixes: 794aa320b79d ("[PATCH] sigfix-2.5.40-D6")
History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.gi
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/87zgq4d5r4.fsf_-_@email.froward.int.ebiederm.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Recently while investigating a problem with rr and signals I noticed
that siglock is dropped in ptrace_signal and get_signal does not jump
to relock.
Looking farther to see if the problem is anywhere else I see that
do_signal_stop also returns if signal_group_exit is true. I believe
that test can now never be true, but it is a bit hard to trace
through and be certain.
Testing signal_group_exit is not expensive, so move the test for
signal_group_exit into the for loop inside of get_signal to ensure
the test is never skipped improperly.
This has been a potential problem since I added the test for
signal_group_exit was added.
Fixes: 35634ffa17 ("signal: Always notice exiting tasks")
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/875yssekcd.fsf_-_@email.froward.int.ebiederm.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Use static_call to optimize perf's guest callbacks on arm64 and x86,
which are now the only architectures that define the callbacks. Use
DEFINE_STATIC_CALL_RET0 as the default/NULL for all guest callbacks, as
the callback semantics are that a return value '0' means "not in guest".
static_call obviously avoids the overhead of CONFIG_RETPOLINE=y, but is
also advantageous versus other solutions, e.g. per-cpu callbacks, in that
a per-cpu memory load is not needed to detect the !guest case.
Based on code from Peter and Like.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20211111020738.2512932-10-seanjc@google.com
Introduce GUEST_PERF_EVENTS and require architectures to select it to
allow registering and using guest callbacks in perf. This will hopefully
make it more difficult for new architectures to add useless "support" for
guest callbacks, e.g. via copy+paste.
Stubbing out the helpers has the happy bonus of avoiding a load of
perf_guest_cbs when GUEST_PERF_EVENTS=n on arm64/x86.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20211111020738.2512932-9-seanjc@google.com
Drop the 'int' return value from the perf (un)register callbacks helpers
and stop pretending perf can support multiple callbacks. The 'int'
returns are not future proofing anything as none of the callers take
action on an error. It's also not obvious that there will ever be
co-tenant hypervisors, and if there are, that allowing multiple callbacks
to be registered is desirable or even correct.
Opportunistically rename callbacks=>cbs in the affected declarations to
match their definitions.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20211111020738.2512932-5-seanjc@google.com
Protect perf_guest_cbs with RCU to fix multiple possible errors. Luckily,
all paths that read perf_guest_cbs already require RCU protection, e.g. to
protect the callback chains, so only the direct perf_guest_cbs touchpoints
need to be modified.
Bug #1 is a simple lack of WRITE_ONCE/READ_ONCE behavior to ensure
perf_guest_cbs isn't reloaded between a !NULL check and a dereference.
Fixed via the READ_ONCE() in rcu_dereference().
Bug #2 is that on weakly-ordered architectures, updates to the callbacks
themselves are not guaranteed to be visible before the pointer is made
visible to readers. Fixed by the smp_store_release() in
rcu_assign_pointer() when the new pointer is non-NULL.
Bug #3 is that, because the callbacks are global, it's possible for
readers to run in parallel with an unregisters, and thus a module
implementing the callbacks can be unloaded while readers are in flight,
resulting in a use-after-free. Fixed by a synchronize_rcu() call when
unregistering callbacks.
Bug #1 escaped notice because it's extremely unlikely a compiler will
reload perf_guest_cbs in this sequence. perf_guest_cbs does get reloaded
for future derefs, e.g. for ->is_user_mode(), but the ->is_in_guest()
guard all but guarantees the consumer will win the race, e.g. to nullify
perf_guest_cbs, KVM has to completely exit the guest and teardown down
all VMs before KVM start its module unload / unregister sequence. This
also makes it all but impossible to encounter bug #3.
Bug #2 has not been a problem because all architectures that register
callbacks are strongly ordered and/or have a static set of callbacks.
But with help, unloading kvm_intel can trigger bug #1 e.g. wrapping
perf_guest_cbs with READ_ONCE in perf_misc_flags() while spamming
kvm_intel module load/unload leads to:
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP
CPU: 6 PID: 1825 Comm: stress Not tainted 5.14.0-rc2+ #459
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:perf_misc_flags+0x1c/0x70
Call Trace:
perf_prepare_sample+0x53/0x6b0
perf_event_output_forward+0x67/0x160
__perf_event_overflow+0x52/0xf0
handle_pmi_common+0x207/0x300
intel_pmu_handle_irq+0xcf/0x410
perf_event_nmi_handler+0x28/0x50
nmi_handle+0xc7/0x260
default_do_nmi+0x6b/0x170
exc_nmi+0x103/0x130
asm_exc_nmi+0x76/0xbf
Fixes: 39447b386c ("perf: Enhance perf to allow for guest statistic collection from host")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211111020738.2512932-2-seanjc@google.com
We've noticed cases where tasks in a cgroup are stalled on memory but
there is little memory FULL pressure since tasks stay on the runqueue
in reclaim.
A simple example involves a single threaded program that keeps leaking
and touching large amounts of memory. It runs in a cgroup with swap
enabled, memory.high set at 10M and cpu.max ratio set at 5%. Though
there is significant CPU pressure and memory SOME, there is barely any
memory FULL since the task enters reclaim and stays on the runqueue.
However, this memory-bound task is effectively stalled on memory and
we expect memory FULL to match memory SOME in this scenario.
The code is confused about memstall && running, thinking there is a
stalled task and a productive task when there's only one task: a
reclaimer that's counted as both. To fix this, we redefine the
condition for PSI_MEM_FULL to check that all running tasks are in an
active memstall instead of checking that there are no running tasks.
case PSI_MEM_FULL:
- return unlikely(tasks[NR_MEMSTALL] && !tasks[NR_RUNNING]);
+ return unlikely(tasks[NR_MEMSTALL] &&
+ tasks[NR_RUNNING] == tasks[NR_MEMSTALL_RUNNING]);
This will capture reclaimers. It will also capture tasks that called
psi_memstall_enter() and are about to sleep, but this should be
negligible noise.
Signed-off-by: Brian Chen <brianchen118@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20211110213312.310243-1-brianchen118@gmail.com
