diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2025-06-05 12:31:45 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-06-27 11:02:58 +0100 |
| commit | 7b8f3c72175c6a63a95cf2e219f8b78e2baad34e (patch) | |
| tree | 12e2485ba75a9cb7500ca986b4416f5f62cc52dd | |
| parent | cc2f923e92a943c52036abf2f82d89775c94ba05 (diff) | |
perf: Fix sample vs do_exit()
[ Upstream commit 4f6fc782128355931527cefe3eb45338abd8ab39 ]
Baisheng Gao reported an ARM64 crash, which Mark decoded as being a
synchronous external abort -- most likely due to trying to access
MMIO in bad ways.
The crash further shows perf trying to do a user stack sample while in
exit_mmap()'s tlb_finish_mmu() -- i.e. while tearing down the address
space it is trying to access.
It turns out that we stop perf after we tear down the userspace mm; a
receipie for disaster, since perf likes to access userspace for
various reasons.
Flip this order by moving up where we stop perf in do_exit().
Additionally, harden PERF_SAMPLE_CALLCHAIN and PERF_SAMPLE_STACK_USER
to abort when the current task does not have an mm (exit_mm() makes
sure to set current->mm = NULL; before commencing with the actual
teardown). Such that CPU wide events don't trip on this same problem.
Fixes: c5ebcedb566e ("perf: Add ability to attach user stack dump to sample")
Reported-by: Baisheng Gao <baisheng.gao@unisoc.com>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250605110815.GQ39944@noisy.programming.kicks-ass.net
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | kernel/events/core.c | 7 | ||||
| -rw-r--r-- | kernel/exit.c | 17 |
2 files changed, 16 insertions, 8 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 7b97be4ed9d0..ecae7c7f895b 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6219,6 +6219,10 @@ perf_sample_ustack_size(u16 stack_size, u16 header_size, if (!regs) return 0; + /* No mm, no stack, no dump. */ + if (!current->mm) + return 0; + /* * Check if we fit in with the requested stack size into the: * - TASK_SIZE @@ -6687,6 +6691,9 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs) const u32 max_stack = event->attr.sample_max_stack; struct perf_callchain_entry *callchain; + if (!current->mm) + user = false; + if (!kernel && !user) return &__empty_callchain; diff --git a/kernel/exit.c b/kernel/exit.c index 56d3a099825f..8cb4a82c4ed3 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -844,6 +844,15 @@ void __noreturn do_exit(long code) tsk->exit_code = code; taskstats_exit(tsk, group_dead); + /* + * Since sampling can touch ->mm, make sure to stop everything before we + * tear it down. + * + * Also flushes inherited counters to the parent - before the parent + * gets woken up by child-exit notifications. + */ + perf_event_exit_task(tsk); + exit_mm(); if (group_dead) @@ -861,14 +870,6 @@ void __noreturn do_exit(long code) exit_thread(tsk); exit_umh(tsk); - /* - * Flush inherited counters to the parent - before the parent - * gets woken up by child-exit notifications. - * - * because of cgroup mode, must be called before cgroup_exit() - */ - perf_event_exit_task(tsk); - sched_autogroup_exit_task(tsk); cgroup_exit(tsk); |