From mboxrd@z Thu Jan 1 00:00:00 1970 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 2AA2A156641 for ; Wed, 15 May 2024 14:43:27 +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=1715784207; cv=none; b=BVi6bXA6ouVcuXh6rglH0jGDZiu518IXT0cXGuUGf4LzrNcXuM6SY6qi6B5FCtWX5cLjVK6iGeBenfEo+M8q7FcikA0VegrGcOjhyyFcEEUC3rkG67HzUn3CYMnjZ6I+CTU6+CnehmHDvPX3jcAjXuLJzesuysF4Vy6bypv81Q8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715784207; c=relaxed/simple; bh=jdiXquXAPPtPajTSj3ryNiWP4Z6gOwf8+7VBRKa5ETE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=r7SfzGMwWfoFcvyUx90mfqzEqdyGY/Gai5AboUoYMDmx7RGsUX3XAc3XzBNcDctLqkbhTqLt238I8hIrBUT6nb2v2AIbVoG73Emf2lo0mj6vxWjx9049tYjsUHxx3zbCaQUNMlOFGzUll3rbcwqJ46xoqWuuLi8pMRygob2GzC8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EbtTKF6Z; 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="EbtTKF6Z" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8BB4C4AF08; Wed, 15 May 2024 14:43:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1715784207; bh=jdiXquXAPPtPajTSj3ryNiWP4Z6gOwf8+7VBRKa5ETE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EbtTKF6ZV0X7RbH+v9/aKJzpPhBbxhP8uPYX1PxxhdU3i46mHXH7VJVO9rRO1D+BX /OsB+zeGrtsd3TlqXWSYjlSzHC+QEVViuRZL9XYTdndfZfIdGzm9TbbgHyiCnboYuq wiykjpgVd3RzXudnv9IlaqMNT+oDwN7i9f9S0Vx9sgKC2fQBgpVFXZzHH/abtrxWkq AAvAhwGDj6qYPfDw65Lhr1tCRR5TCPXk5S2l62XlM+fAO59hBdiU0kbsnfmuSKRSuP F06kVmLsM+x8/iliNtOZECtsLwRbHEoYHI1NbVRxYB2WFjryM+LZd2WWPQghvoCB/G 5244qLLb76msg== 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 , Sebastian Andrzej Siewior Subject: [PATCH 3/4] perf: Fix event leak upon exit Date: Wed, 15 May 2024 16:43:10 +0200 Message-ID: <20240515144311.16038-4-frederic@kernel.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240515144311.16038-1-frederic@kernel.org> References: <20240515144311.16038-1-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: 8bit 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 = pending_id; irq_work_queue(&event->pending_irq); =========> PREEMPTION: TASK A -> TASK B event_sched_out() event->pending_sigtrap = 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 = -1 [...] =========> TASK B -> TASK A perf_event_exit_task(tsk) perf_event_exit_event() free_event() WARN(atomic_long_cmpxchg(&event->refcount, 1, 0) != 1) // leak event due to unexpected refcount == 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 perf_event_context *ctx) event->pending_sigtrap = 0; if (state != PERF_EVENT_STATE_OFF && !event->pending_work) { - event->pending_work = 1; - dec = 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) >= 0) { + WARN_ON_ONCE(!atomic_long_inc_not_zero(&event->refcount)); + dec = false; + event->pending_work = 1; + } } if (dec) local_dec(&event->ctx->nr_pending); -- 2.44.0