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 576CC189522; Tue, 30 Jul 2024 17:08:49 +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=1722359329; cv=none; b=DkHa7y1dyYU/RZu8kQVnXL/0e1McQf27BNwTX6DXU6PXfNltQaHJpUuz3FYY/l8kRtXxyC50FeTU5Xz7k3k4KiaDDdoett0ucpEyozm3tulAZ5VwGhzAgTarZ3olo2JXLG72/Ge9G7li7YUrdJ+0bgSaEjYIXqoDpS0EjR1Ve7E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722359329; c=relaxed/simple; bh=8m0+fAFCWACtj9dIzK9Tc5s3HAKFkymCHlGX7R8qmSM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sS541PgOm9dMsGx7rvzlf/0O76jfcTY+3jVEMSx+YuZgL2KtmpVKnB7Ol/ZjwPskLxVcW04DnBzJfgBVOcJZ+HoJKHocOM0OErNXN3BVaZtim9BXgOQ5RDZXxbeHsZf0dFizCbRMwgxhSwCOXhD/f19CSU01/S+QhM7GHKcZQCc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=yU1niHeU; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="yU1niHeU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C6411C32782; Tue, 30 Jul 2024 17:08:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1722359329; bh=8m0+fAFCWACtj9dIzK9Tc5s3HAKFkymCHlGX7R8qmSM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yU1niHeUCiHySbqOEyiZKIVi6cKBb7meRAgcB5qdUf3BMDIDTd+nWKfEZudbx8y1x Tebci8Aq1dmg0mg8hN5RkdX53dP6+NaH5F8Z5bie/p1bedgX1f8AROA7vbhQrom7RP kuQi4EcUNOvjIdhOMetJGIp1Z8zoTDFlHrlzO7mQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Frederic Weisbecker , "Peter Zijlstra (Intel)" Subject: [PATCH 6.6 467/568] perf: Fix event leak upon exit Date: Tue, 30 Jul 2024 17:49:34 +0200 Message-ID: <20240730151658.272549273@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240730151639.792277039@linuxfoundation.org> References: <20240730151639.792277039@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Frederic Weisbecker commit 2fd5ad3f310de22836cdacae919dd99d758a1f1b upstream. 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 an 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 Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240621091601.18227-4-frederic@kernel.org Signed-off-by: Greg Kroah-Hartman --- kernel/events/core.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2284,18 +2284,15 @@ event_sched_out(struct perf_event *event } if (event->pending_sigtrap) { - bool dec = true; - event->pending_sigtrap = 0; if (state != PERF_EVENT_STATE_OFF && - !event->pending_work) { - event->pending_work = 1; - dec = false; + !event->pending_work && + !task_work_add(current, &event->pending_task, TWA_RESUME)) { WARN_ON_ONCE(!atomic_long_inc_not_zero(&event->refcount)); - task_work_add(current, &event->pending_task, TWA_RESUME); - } - if (dec) + event->pending_work = 1; + } else { local_dec(&event->ctx->nr_pending); + } } perf_event_set_state(event, state);