From nobody Fri Dec 19 17:18:57 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 5A2F459168; Mon, 1 Jul 2024 07:14:54 +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=1719818095; cv=none; b=c8h8/VifPtdcwyb1W9nH5pC2mlH5mC8Z44lKPsPDjAQvtY2KH36RkX2cP39RufwYgSFI3SpTa4w87vdkyCpk+oxg/s3zKfSfG7Ul1ymPJ+vXOBDjIL5GxtF8UowvLudo+WEdqL+abIRasG1/wVFYV37p4pQnIH+uxwqZmq4eGo4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719818095; c=relaxed/simple; bh=aBKD3Uj+bz0fC3jHCQStdgSfgrblCRNumgZ6FJr+Qg4=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=TGdW/6F8KzhneTXWz2x4PnSOwHUAHOzXQQ6xpCAtLpKxutzkwqTSu5T/pi8sZ+zFCP6lt377X0syfFy8aRczoGAZobT2nUzGDG0AG2XB0ePq+PlF3+KjQfDourae+1Gt2yHhNxq1CQf2hzg5XDeC3IIRZJdsKT471ZWkCNFgJyQ= 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=zZE2gWH8; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=uSMUdtpO; 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="zZE2gWH8"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="uSMUdtpO" Date: Mon, 01 Jul 2024 07:14:52 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1719818092; 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=/8y7doyPNcQhto4gUcbOsO9PzfLioSsTJraVqqEFPzo=; b=zZE2gWH8Ta4XTVNDi/qT7kZ/8t6w2R7CmoErQXWQt4o4/4W5mVZ9MLNHaM0hryfK8EkPsG yV05olVQTIV1nZHnkJjWixxpR3DSHXZxywrFstNArpe+VfQTw++AcTN2KKgWQfMMQtu/OV rWEGXYQsCqPFfd63Rv+bth7FIARe4vhK2rMOJNE2Prlbja3TYdZEYvdzBfWOcJRh4Ypegm KF15GZETcCElMj5p2ne+kjk0JO3ynlCcodtxHujR6nLL6qT2hmbuRrEWP/AuMt6J4m9uAh WbIY2EAUNtpK1cyEJ6jFnmy4Stx6vtd3kVJm7SvTzo9qWz3HbRFlxihG2cPoVw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1719818092; 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=/8y7doyPNcQhto4gUcbOsO9PzfLioSsTJraVqqEFPzo=; b=uSMUdtpODs3m7FqMhv7dxTVrymrLyQC3dAsnpDmlZzDr5RYY+q+Mj+kuXNAsr2wBb+7A+B 9zkMzjINT0CZUUDQ== 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/urgent] perf: Fix event leak upon exit Cc: Frederic Weisbecker , "Peter Zijlstra (Intel)" , 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: <171981809242.2215.6810968999368920588.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/urgent branch of tip: Commit-ID: 73caafba7021a97c22bff58c3d123228e03cdc46 Gitweb: https://git.kernel.org/tip/73caafba7021a97c22bff58c3d123228e= 03cdc46 Author: Frederic Weisbecker AuthorDate: Fri, 21 Jun 2024 11:16:00 +02:00 Committer: Peter Zijlstra CommitterDate: Tue, 25 Jun 2024 10:43:38 +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) 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 8f908f0..7c3218d 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);