linux-kernel - [PATCH] perf/core: Fix WARN in perf

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Message-ID: <f8dee957-d286-421d-976a-c0c580454fb3@I-love.SAKURA.ne.jp>
Date: Sat, 5 Jul 2025 23:43:37 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: syzbot <syzbot+2fe61cb2a86066be6985@...kaller.appspotmail.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-perf-users@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] perf/core: Fix WARN in perf_sigtrap()

Since commit 4f6fc7821283 ("perf: Fix sample vs do_exit()") has moved
perf_event_exit_task() call from after exit_task_work() to before
exit_task_work(), task_work_add() from perf_event_exit_task() now returns
0 than -ESRCH, despite perf_event_exit_task_context() updates ctx->task
to TASK_TOMBSTONE. As a result, event->ctx->task == current assumption
no longer holds.

Reported-by: syzbot <syzbot+2fe61cb2a86066be6985@...kaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=2fe61cb2a86066be6985
Fixes: 4f6fc7821283 ("perf: Fix sample vs do_exit()")
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
#syz test

 kernel/events/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 7281230044d0..489f42defe3c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7208,7 +7208,8 @@ static void perf_sigtrap(struct perf_event *event)
 	 * ctx->task or current has changed in the meantime. This can be the
 	 * case on architectures that do not implement arch_irq_work_raise().
 	 */
-	if (WARN_ON_ONCE(event->ctx->task != current))
+	if (WARN_ON_ONCE(event->ctx->task != current &&
+			 event->ctx->task != TASK_TOMBSTONE))
 		return;
 
 	/*
-- 
2.50.0