From: bot+bpf-ci@kernel.org
To: kartikey406@gmail.com,peterz@infradead.org,mingo@redhat.com,acme@kernel.org,namhyung@kernel.org,mark.rutland@arm.com,alexander.shishkin@linux.intel.com,jolsa@kernel.org,irogers@google.com,adrian.hunter@intel.com,james.clark@linaro.org,song@kernel.org,ast@kernel.org,daniel@iogearbox.net,andrii@kernel.org,eddyz87@gmail.com,memxor@gmail.com,martin.lau@linux.dev,yonghong.song@linux.dev,emil@etsalapatis.com,kpsingh@kernel.org,mattbobrowski@google.com,rostedt@goodmis.org,mhiramat@kernel.org,mathieu.desnoyers@efficios.com,me@kylehuey.com
Cc: linux-perf-users@vger.kernel.org,linux-kernel@vger.kernel.org,bpf@vger.kernel.org,linux-trace-kernel@vger.kernel.org,kartikey406@gmail.com,syzbot+651d2774bd1d8395595f@syzkaller.appspotmail.com,ast@kernel.org,andrii@kernel.org,daniel@iogearbox.net,martin.lau@kernel.org,eddyz87@gmail.com,yonghong.song@linux.dev,clm@meta.com,ihor.solodrai@linux.dev
Subject: Re: [PATCH] perf/bpf: Fix data race in __perf_event_overflow
Date: Wed, 12 Aug 2026 01:04:37 +0000 (UTC) [thread overview]
Message-ID: <42d2df770e6e5f9134476509f690ec9b7d68f0da4cd1ffadcf3f9c1b75f0adf2@mail.kernel.org> (raw)
In-Reply-To: <20260811235331.10044-1-kartikey406@gmail.com>
[-- Attachment #1: Type: text/plain, Size: 1931 bytes --]
> commit ffa161d3558e4937793a0c3e98e19e4b22e58bd9
> Author: Deepanshu Kartikey <kartikey406@gmail.com>
> Date: Wed Aug 12 05:23:31 2026 +0530
>
> perf/bpf: Fix data race in __perf_event_overflow
>
> perf_event_detach_bpf_prog() writes event->prog = NULL
> under bpf_event_mutex, while __perf_event_overflow() reads
> event->prog concurrently without any lock protection. This
> causes a data race detected by KCSAN.
>
> __perf_event_overflow() can be called from interrupt/NMI
> context, so it cannot acquire bpf_event_mutex. Fix the race
> by using WRITE_ONCE() in perf_event_detach_bpf_prog() and
> READ_ONCE() in __perf_event_overflow(). Also store the result
> of READ_ONCE() in a local variable to avoid reading event->prog
> twice which could result in a NULL pointer dereference if the
> pointer becomes NULL between the two reads.
>
> Reported-by: syzbot+651d2774bd1d8395595f@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=651d2774bd1d8395595f
> Fixes: f11f10bfa1ca ("perf/bpf: Call BPF handler directly, not through overflow machinery")
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
> Reported-by: syzbot+651d2774bd1d8395595f@syzkaller.appspotmail.com
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
The trailer block contains duplicate tags: both Reported-by: and
Signed-off-by: appear twice. Also, the second Reported-by: is placed
after the first Signed-off-by:, which breaks the conventional trailer
ordering (Reported-by/Closes/Fixes should come before Signed-off-by).
Should the duplicates be collapsed to one of each, in proper trailer order?
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/31550171807
next prev parent reply other threads:[~2026-08-12 1:04 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-11 23:53 Deepanshu Kartikey
2026-08-12 1:04 ` bot+bpf-ci [this message]
2026-08-12 10:12 ` Peter Zijlstra
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