From nobody Mon Feb 9 15:07:27 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C54F713F01B for ; Fri, 29 Mar 2024 23:58:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711756728; cv=none; b=lXlVF6xVvaFU8KLAuM2wvju+RGhK9Xlp485RF6x+gDdz3D5URNIzfwRhSf3/Cnrp3rBU9NWKQgjwsD6WFhnFNQ7XEKpcHyfcBTmiiUhCjYs8GG4Mis5r6K5KJZ/jFZi+Z5MZZBK1o9OqZJL149oeEFjKSFafi15gz7OuT40pAoM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711756728; c=relaxed/simple; bh=jdiXquXAPPtPajTSj3ryNiWP4Z6gOwf8+7VBRKa5ETE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bRoLAycOvLeo16XTi9CUCWvcVKoKKd05G5U6PGqS8uUabaNwnAJSsQme6pW/tpaRE6lzvE5q04nR+GbNL5DTpiIC8Q6oEmdSyxVIArGTSwlRlKO8zzqRsbYpxP9jfQGZqSp4KTkshz41UHjnu6KEokRaP/mvwIqiB0K1/GlEwv8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZNXj0OHr; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZNXj0OHr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EE78AC433B1; Fri, 29 Mar 2024 23:58:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711756728; bh=jdiXquXAPPtPajTSj3ryNiWP4Z6gOwf8+7VBRKa5ETE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZNXj0OHrqHocYTHj5KYi2Dvp4W1KeU6L284QF6RtRSMRQJnDVgK+IyAc1OQyx+7uc 9fgQDvLn1UmxLcaPxbyEpXaYyjV/3fv3Oven2GCWjiWfyn9uflPOzqTPpt9EPdG19M A70Pn5KvlNooPN1PoLiDr2UMqTxY+RAhPBoY1RHF3XoyLVtoiMN9Mg6ik1W/dnb0Ob QHrKDcejZSqvPNkes92IvfsXut5youx7rMSb4c6qKAIcf+lrIeEarhEWZn56/GkLqr /k+1DvDz+MQciUAvUuGEO2Gt4iFhchQJEzrhh24uB6dnFqT5wxpSqKSMjgFitKbUvA mTFMg45v2mr5Q== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter Subject: [PATCH 3/4] perf: Fix event leak upon exit Date: Sat, 30 Mar 2024 00:58:11 +0100 Message-ID: <20240329235812.18917-4-frederic@kernel.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240329235812.18917-1-frederic@kernel.org> References: <20240329235812.18917-1-frederic@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When a task is scheduled out, pending sigtrap deliveries are deferred to the target task upon resume to userspace via task_work. However failures while adding en event's callback to the task_work engine are ignored. And since the last call for events exit happen after task work is eventually closed, there is a small window during which pending sigtrap can be queued though ignored, leaking the event refcount addition such as in the following scenario: TASK A ----- do_exit() exit_task_work(tsk); perf_event_overflow() event->pending_sigtrap =3D pending_id; irq_work_queue(&event->pending_irq); =3D=3D=3D=3D=3D=3D=3D=3D=3D> PREEMPTION: TASK A -> TASK B event_sched_out() event->pending_sigtrap =3D 0; atomic_long_inc_not_zero(&event->refcount) // FAILS: task work has exited task_work_add(&event->pending_task) [...] perf_pending_irq() // early return: event->oncpu =3D -1 [...] =3D=3D=3D=3D=3D=3D=3D=3D=3D> TASK B -> TASK A perf_event_exit_task(tsk) perf_event_exit_event() free_event() WARN(atomic_long_cmpxchg(&event->refcount, 1, 0) !=3D 1) // leak event due to unexpected refcount =3D=3D 2 As a result the event is never released while the task exits. Fix this with appropriate task_work_add()'s error handling. Fixes: 517e6a301f34 ("perf: Fix perf_pending_task() UaF") Signed-off-by: Frederic Weisbecker --- kernel/events/core.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 724e6d7e128f..c1632e69c69d 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2289,10 +2289,11 @@ event_sched_out(struct perf_event *event, struct pe= rf_event_context *ctx) event->pending_sigtrap =3D 0; if (state !=3D PERF_EVENT_STATE_OFF && !event->pending_work) { - event->pending_work =3D 1; - dec =3D false; - WARN_ON_ONCE(!atomic_long_inc_not_zero(&event->refcount)); - task_work_add(current, &event->pending_task, TWA_RESUME); + if (task_work_add(current, &event->pending_task, TWA_RESUME) >=3D 0) { + WARN_ON_ONCE(!atomic_long_inc_not_zero(&event->refcount)); + dec =3D false; + event->pending_work =3D 1; + } } if (dec) local_dec(&event->ctx->nr_pending); --=20 2.44.0