From nobody Thu Dec 18 05:17:28 2025 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 0337C15B0E1; Tue, 9 Jul 2024 11:42:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720525323; cv=none; b=Be365UOGc0aioCF6ZKTimuEEZG4mFyFg+yPDD2RIlkPW0bMQGq5TqI2BKbdrhKCcFz12PTm840EFzr9cHlvCdAivB/bYkZneKc5tUf9khWZnn/0H+3gJJ9i6mn3ViNmyv5ZDE59P7cwvPUFffftH8G0DthqUe0BTwlGVnwCQXJI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720525323; c=relaxed/simple; bh=GEnUgTu8lPUb9sbiJtAnklk56wz/FMBgSpidCD4+D88=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=JsqBVWiLwHQZ74f307m1adDLigTathuOB3mfSmGmWw67pBTL84qwx8/xSTRacKJjwdMgYV2XR3p9UsESvBMiz/wtcHmrluOG8jl1elwXRnVpB9fy60Sp+/JzQnI8DRVT8rcFbz4xkw3CbSGCp9RbD3TPECYl0T23saGb7TzZkzE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=T8GXWA+q; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=ByZrffwF; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="T8GXWA+q"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="ByZrffwF" Date: Tue, 09 Jul 2024 11:42:00 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1720525320; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=LG4ihRH27yiQythiXxJ5u6cgg3+Qi+eGSXh3MeksO2E=; b=T8GXWA+qtJOg+okNZf9b3whQ9tfJZF4ZXDfBvp2AfxBn0177gt6NsrEEaruniMvJ0w0aMv mwOX9cn99FNunASUFAKZyEBkcXsllsY20Ufo+2wq5UxfVHWsDI93UwfVVvmre7AFlFMVoI lOxrPjVN7bP+4OYelPAqaAaJYdfy9J44p8bXu55V41GVJaXlpQfEotbT64eZpxuyVvSz++ 5x2ir4JcFf2FXXFDC94kr5OeWqnPSjzBkOMc+zoWYt4GrHCcB3MaLf5Ub3UeyJW3M8xk+U O59ffgiG9t9GfIM8Y6emru2Kb+JPt92PavH658vEiqJV+LNMS5TJvz5hQ+0JNA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1720525320; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=LG4ihRH27yiQythiXxJ5u6cgg3+Qi+eGSXh3MeksO2E=; b=ByZrffwFwgqCGudPPiA6ZTaq9CR00i7Z/oHxTnxa5t6hcWXsR5HHX1Gd5yl6zTnrWTSbXL PkyfMiDxUmMYfyCQ== From: "tip-bot2 for Frederic Weisbecker" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: perf/core] perf: Fix event leak upon exit Cc: Frederic Weisbecker , "Peter Zijlstra (Intel)" , stable@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20240621091601.18227-4-frederic@kernel.org> References: <20240621091601.18227-4-frederic@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <172052532020.2215.3558915435239309013.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the perf/core branch of tip: Commit-ID: 2fd5ad3f310de22836cdacae919dd99d758a1f1b Gitweb: https://git.kernel.org/tip/2fd5ad3f310de22836cdacae919dd99d7= 58a1f1b Author: Frederic Weisbecker AuthorDate: Fri, 21 Jun 2024 11:16:00 +02:00 Committer: Peter Zijlstra CommitterDate: Tue, 09 Jul 2024 13:26:33 +02:00 perf: Fix event leak upon exit 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 =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 Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240621091601.18227-4-frederic@kernel.org --- kernel/events/core.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 51ce436..576400d 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2284,18 +2284,15 @@ event_sched_out(struct perf_event *event, struct pe= rf_event_context *ctx) } =20 if (event->pending_sigtrap) { - bool dec =3D true; - event->pending_sigtrap =3D 0; if (state !=3D PERF_EVENT_STATE_OFF && - !event->pending_work) { - event->pending_work =3D 1; - dec =3D 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 =3D 1; + } else { local_dec(&event->ctx->nr_pending); + } } =20 perf_event_set_state(event, state);