Messages in this thread Patch in this message | | | Date | Thu, 27 May 2021 12:47:11 +0200 | Subject | [PATCH] perf: Fix data race between pin_count increment/decrement | From | Marco Elver <> |
| |
KCSAN reports a data race between increment and decrement of pin_count:
write to 0xffff888237c2d4e0 of 4 bytes by task 15740 on cpu 1: find_get_context kernel/events/core.c:4617 __do_sys_perf_event_open kernel/events/core.c:12097 [inline] __se_sys_perf_event_open kernel/events/core.c:11933 ... read to 0xffff888237c2d4e0 of 4 bytes by task 15743 on cpu 0: perf_unpin_context kernel/events/core.c:1525 [inline] __do_sys_perf_event_open kernel/events/core.c:12328 [inline] __se_sys_perf_event_open kernel/events/core.c:11933 ...
Because neither read-modify-write here is atomic, this can lead to one of the operations being lost, resulting in an inconsistent pin_count. Fix it by adding the missing locking in the CPU-event case.
Reported-by: syzbot+142c9018f5962db69c7e@syzkaller.appspotmail.com Signed-off-by: Marco Elver <elver@google.com> --- kernel/events/core.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 6fee4a7e88d7..fe88d6eea3c2 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4609,7 +4609,9 @@ find_get_context(struct pmu *pmu, struct task_struct *task, cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu); ctx = &cpuctx->ctx; get_ctx(ctx); + raw_spin_lock_irqsave(&ctx->lock, flags); ++ctx->pin_count; + raw_spin_unlock_irqrestore(&ctx->lock, flags); return ctx; } -- 2.31.1.818.g46aad6cb9e-goog
| |