Re: [PATCH v3] perf/core: Don't send SIGTRAP after exec removed the event

[sashiko-bot@kernel.org]

> A sigtrap event must also set remove_on_exec, so that its SIGTRAP never
> reaches a program after exec. But the signal is sent from task work,
> which only runs on the way back to user space. If the event overflows
> shortly before execve(), the task work can still be pending when the
> task enters execve(), and then runs when execve() returns. By then
> perf_event_exec() has removed the event and the new program has default
> signal handlers, so the SIGTRAP kills it.
> 
> The exec_stress test in the remove_on_exec selftest catches this and
> fails about half the time in a VM. A process that opens a sigtrap event
> on itself and then calls execve() is killed by SIGTRAP in 15% to 50% of
> runs, both on an AMD machine running v7.2 and in a VM, with or without
> close-on-exec on the event fd.
> 
> Commit ffb684f2aa14 ("perf: Fix race between perf_event_exit_task() and
> [ ... ]
> 
> Fixes: 97ba62b27867 ("perf: Add support for SIGTRAP on perf events")
> Cc: stable@vger.kernel.org
> Assisted-by: LLM
> Signed-off-by: Danish Khateeb <danishkhateeb03@gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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