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Thu, 13 Nov 2025 19:34:17 -0800 (PST) From: Liangyan To: peterz@infradead.org, mingo@redhat.com, bigeasy@linutronix.de Cc: 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, zengxianjun@bytedance.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, Liangyan Subject: [PATCH v3] perf/core: Fix pending work re-queued in __perf_event_overflow Date: Fri, 14 Nov 2025 11:33:49 +0800 Message-Id: <20251114033349.3048-1-liangyan.peng@bytedance.com> X-Mailer: git-send-email 2.39.3 (Apple Git-145) In-Reply-To: <20251109164122.80138-1-liangyan.peng@bytedance.com> References: <20251109164122.80138-1-liangyan.peng@bytedance.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit We got warning below during perf test. [ 467.100914] [ T1] WARNING: CPU: 0 PID: 1 at kernel/events/core.c:5147 put_pmu_ctx+0x2ef/0x3c0 [ 467.107702] [ T1] CPU: 0 UID: 0 PID: 1 Comm: systemd Kdump: loaded Tainted: G E 6.18.0-rc4-dirty #114 PREEMPT(voluntary) [ 467.109835] [ T1] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 [ 467.111027] [ T1] RIP: 0010:put_pmu_ctx+0x2ef/0x3c0 [ 467.122081] [ T1] Call Trace: [ 467.122463] [ T1] [ 467.124822] [ T1] __free_event+0x337/0xa50 [ 467.125306] [ T1] perf_pending_task+0x10f/0x3b0 [ 467.125824] [ T1] task_work_run+0x140/0x210 [ 467.127413] [ T1] exit_to_user_mode_loop+0x10e/0x130 [ 467.127965] [ T1] do_syscall_64+0x26d/0x2e0 [ 467.128453] [ T1] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 467.129025] [ T1] RIP: 0033:0x7f01d22349ca [ 467.135157] [ T1] A race condition occurs between task context and IRQ context when handling sigtrap tracepoint event overflows: 1. In task context, an event is overflowed and its pending work is queued to task->task_works 2. Before pending_work is set, the same event overflows in IRQ context 3. Both contexts queue the same perf pending work to task->task_works This double queuing causes: - task_work_run() enters infinite loop calling perf_pending_task() - Potential warnings and use-after-free when event is freed in perf_pending_task() Fix the race by disabling interrupts during queuing of perf pending work. Fixes: c5d93d23a260 ("perf: Enqueue SIGTRAP always via task_work.") Reported-by: Xianjun Zeng Signed-off-by: Liangyan --- v3: Refine commit log suggested by Sebastian. --- kernel/events/core.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index cae921f4d137..7c63e5fdd334 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -10433,6 +10433,16 @@ static int __perf_event_overflow(struct perf_event *event, notify_mode = in_nmi() ? TWA_NMI_CURRENT : TWA_RESUME; + /* + * Task context queues the work via task_work_add() but has not yet + * set event->pending_work when the same event overflows in + * IRQ context. The IRQ path, seeing !event->pending_work, + * queues the work again. + * The double queuing causes corruption in task->task_works. + * Prevent this by disabling interrupts around the critical section. + */ + guard(irqsave)(); + if (!event->pending_work && !task_work_add(current, &event->pending_task, notify_mode)) { event->pending_work = pending_id; -- 2.39.3 (Apple Git-145)