Re: [PATCH] perf/core: Prevent duplicate sigtrap task work enqueue

[Sebastian Andrzej Siewior]

On 2026-10-31 11:45:20 [+0000], Tengda Wu wrote:
> The sigtrap handling in __perf_event_overflow() checks
> event->pending_work before calling task_work_add(), but only sets
> pending_work after the task work has been queued.
> 
> This leaves a window where an NMI can interrupt task_work_add()
> and re-enter __perf_event_overflow() for the same event. Since
> pending_work is still zero, the nested invocation can enqueue
> the same pending_task again.
> 
> The re-entrant call path is:
> 
>   __perf_event_overflow()
>     task_work_add()
>       kasan_record_aux_stack()
>         <NMI>
>           __perf_event_overflow()
>             task_work_add()

How was the issue identified?

Sebastian