From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753738AbeE3LmK (ORCPT ); Wed, 30 May 2018 07:42:10 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:60716 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752075AbeE3LG7 (ORCPT ); Wed, 30 May 2018 07:06:59 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Takashi Iwai" Date: Wed, 30 May 2018 11:52:42 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 139/153] ALSA: aloop: Fix access to not-yet-ready substream via cable In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.102-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit 8e6b1a72a75bb5067ccb6b56d8ca4aa3a300a64e upstream. In loopback_open() and loopback_close(), we assign and release the substream object to the corresponding cable in a racy way. It's neither locked nor done in the right position. The open callback assigns the substream before its preparation finishes, hence the other side of the cable may pick it up, which may lead to the invalid memory access. This patch addresses these: move the assignment to the end of the open callback, and wrap with cable->lock for avoiding concurrent accesses. Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings --- sound/drivers/aloop.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/sound/drivers/aloop.c +++ b/sound/drivers/aloop.c @@ -656,7 +656,9 @@ static void free_cable(struct snd_pcm_su return; if (cable->streams[!substream->stream]) { /* other stream is still alive */ + spin_lock_irq(&cable->lock); cable->streams[substream->stream] = NULL; + spin_unlock_irq(&cable->lock); } else { /* free the cable */ loopback->cables[substream->number][dev] = NULL; @@ -697,7 +699,6 @@ static int loopback_open(struct snd_pcm_ loopback->cables[substream->number][dev] = cable; } dpcm->cable = cable; - cable->streams[substream->stream] = dpcm; snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS); @@ -729,6 +730,11 @@ static int loopback_open(struct snd_pcm_ runtime->hw = loopback_pcm_hardware; else runtime->hw = cable->hw; + + spin_lock_irq(&cable->lock); + cable->streams[substream->stream] = dpcm; + spin_unlock_irq(&cable->lock); + unlock: if (err < 0) { free_cable(substream);