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Sat, 03 Oct 2026 13:26:03 -0700 (PDT) From: vineash To: stable@vger.kernel.org Cc: penguin-kernel@I-love.SAKURA.ne.jp, linux-perf-users@vger.kernel.org Subject: Request to backport "perf/core: Fix WARN in perf_sigtrap()" to 6.12.y, 6.6.y, 6.1.y and 5.15.y Date: Sun, 04 Oct 2026 04:25:31 +0800 Message-ID: <179105913174.1859134.5466929391582828993@gmail.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Hi, Please consider backporting the following upstream commit to the 6.12.y, 6.6.y, 6.1.y and 5.15.y stable trees: 3da6bb419750 ("perf/core: Fix WARN in perf_sigtrap()") It was picked up by AUTOSEL for these trees on 2025-07-14 and nobody objected, but it never got into any of them. As of 2026-10-03, linux-6.12.y, linux-6.6.y, linux-6.1.y and linux-5.15.y still have the old check order in perf_sigtrap(). linux-6.18.y already has the fix. The WARN is still reachable on 6.12.110. A syzkaller C reproducer triggers it from the exit path: WARNING: CPU: 1 PID: 1904 at kernel/events/core.c:6908 perf_pending_task+0x368/0x430 task_work_run+0x14e/0x250 do_exit+0xb5d/0x2ca0 do_group_exit+0xd3/0x2a0 get_signal+0x2791/0x2800 This is the scenario the commit describes: exit_task_work() runs after perf_event_exit_task_context() has set ctx->task to TASK_TOMBSTONE. Testing on 6.12.110 (QEMU/KVM, x86_64, same .config for both kernels): - unpatched: the reproducer triggered the WARN in 3 of 3 runs, each within about 30 s - with 3da6bb419750 cherry-picked (applies cleanly, offset only): no WARN in 3 of 3 runs of 240-300 s each I only tested 6.12.y. For the other trees I only checked that the fix is missing. I found this while triaging syzkaller crashes. An LLM-based assistant helped with the analysis and ran the tests described above. Thanks, vineash