From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-886641-1526503915-2-772741062660279094 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no ("Email failed DMARC policy for domain") X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.248, MAILING_LIST_MULTI -1, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='US', FromHeader='uk', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-IgnoreVacation: yes ("Email failed DMARC policy for domain") X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=fm2; t= 1526503914; b=HiNdH7dCxZZadZ6NVt7IQIX720aiKGHEc7NTe43ElbQoe8K4zB Qsr4j3J4sjunVBSQjvGf3+HAK4b+axY+Wuh83Jo6SYTd6jUdqZXSxP/gYnpujVbe hutFvnhX2rMr1XzvoyZGm/C0X91B7xXEQlMkBMP/MXE9ewFD97i63umUmo9HAVvS 7SYszKv1lBiRHTfRSmrSg6OGQrqDRa0dGJHhKceB9Bioi0CNV6hjU9bN0vSxTJRi c6t155or7tTvmjVBdMqtIUSR6DxM/cbG3Szrfg+lhzkPxI+9zepw4TBzGSDwIXZK 06bZB/z8TJ82PSGjCxjjkKwOQtu2S7U/o5Hw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=message-id:subject:from:to:cc:date :in-reply-to:references:content-type:mime-version :content-transfer-encoding:sender:list-id; s=fm2; t=1526503914; bh=tzN6wLySpiVeoVnxOVpmj9FkyYgWEi8hw/29G00NfQg=; b=KlkfCdINQ6JA RD7TSI7XQkD+V/C67SYIWPDvjKzoIJqQf8vP2m/vZkm0bT7Dm+7scRdpV98sI5+1 w64bIaRICD/L27WN4aWUn7zkzN0S1Lq8JStEC8iCeKxImLKpZeo9l4RUHrelFpE/ LQVoB592v50VscjkXLVA4cRIJq5TUvdX8E5UaRwCfGVtlsylY2RBX9K+3NFym4/3 BLjyLceaqgq2wccQThjlLBO9f3TLZXqX/lnI8/OmldfG21WRxqKHfvbh7BmOnKOU qnFmnUWqBQf8+yNesokfa+D27x8IFur9ERbBd62MKmvPCQCtgOnzS8MOyYWAnFXA b35VO0cC9A== ARC-Authentication-Results: i=1; mx3.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=codethink.co.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=codethink.co.uk header.result=pass header_is_org_domain=yes; x-vs=clean score=-100 state=0 Authentication-Results: mx3.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=codethink.co.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=codethink.co.uk header.result=pass header_is_org_domain=yes; x-vs=clean score=-100 state=0 X-ME-VSCategory: clean X-CM-Envelope: MS4wfOAAmPISr65I+biCUuz4x7GpCvPbu1xfp8tZqXbrirCDUW4OnNTmUpqRCKpguKO/R2kYnUZaQr2MfHRb3lnXEgEDSLZ1X203qrCnxmoCFkVCKv5y+XxN ya8POxO5gLGbqfjo25LZLrPZsDA5vrdar+EZG0ddZoLQZWjOrcVlsQaridcOWPqT0NGFXGssMua0lxgprTlh6Crjo1HBZsdjd6adDbvtvf5uLoq71plUiGPY X-CM-Analysis: v=2.3 cv=Tq3Iegfh c=1 sm=1 tr=0 a=UK1r566ZdBxH71SXbqIOeA==:117 a=UK1r566ZdBxH71SXbqIOeA==:17 a=IkcTkHD0fZMA:10 a=VUJBJC2UJ8kA:10 a=rTDo_5_6WMYnJkmuBBkA:9 a=QEXdDO2ut3YA:10 X-ME-CMScore: 0 X-ME-CMCategory: none Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751379AbeEPUvw (ORCPT ); Wed, 16 May 2018 16:51:52 -0400 Received: from imap1.codethink.co.uk ([176.9.8.82]:51429 "EHLO imap1.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751370AbeEPUvv (ORCPT ); Wed, 16 May 2018 16:51:51 -0400 Message-ID: <1526503907.9159.150.camel@codethink.co.uk> Subject: Re: [PATCH 4.4 53/97] ALSA: pcm: Fix UAF at PCM release via PCM timer access From: Ben Hutchings To: Greg Kroah-Hartman , linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, syzbot+8e62ff4e07aa2ce87826@syzkaller.appspotmail.com, Takashi Iwai Date: Wed, 16 May 2018 21:51:47 +0100 In-Reply-To: <20180422135308.244077643@linuxfoundation.org> References: <20180422135304.577223025@linuxfoundation.org> <20180422135308.244077643@linuxfoundation.org> Organization: Codethink Ltd. Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1+deb9u1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Sun, 2018-04-22 at 15:53 +0200, Greg Kroah-Hartman wrote: > 4.4-stable review patch.  If anyone has any objections, please let me know. > > ------------------ > > From: Takashi Iwai > > commit a820ccbe21e8ce8e86c39cd1d3bc8c7d1cbb949b upstream. > > The PCM runtime object is created and freed dynamically at PCM stream > open / close time.  This is tracked via substream->runtime, and it's > cleared at snd_pcm_detach_substream(). > > The runtime object assignment is protected by PCM open_mutex, so for > all PCM operations, it's safely handled.  However, each PCM substream > provides also an ALSA timer interface, and user-space can access to > this while closing a PCM substream.  This may eventually lead to a > UAF, as snd_pcm_timer_resolution() tries to access the runtime while > clearing it in other side. > > Fortunately, it's the only concurrent access from the PCM timer, and > it merely reads runtime->timer_resolution field.  So, we can avoid the > race by reordering kfree() and wrapping the substream->runtime > clearance with the corresponding timer lock. [...] This seems to depend on: commit f65e0d299807d8a11812845c972493c3f9a18e10 Author: Takashi Iwai Date:   Wed Feb 10 12:47:03 2016 +0100     ALSA: timer: Call notifier in the same spinlock (But I'm not totally convinced that snd_pcm_timer_resolution() is always called with the timer lock held, even after that.) Ben. -- Ben Hutchings Software Developer, Codethink Ltd.