From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932140AbcBKN7u (ORCPT ); Thu, 11 Feb 2016 08:59:50 -0500 Received: from mx2.suse.de ([195.135.220.15]:49310 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753305AbcBKN7q (ORCPT ); Thu, 11 Feb 2016 08:59:46 -0500 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Takashi Iwai , Jiri Slaby Subject: [PATCH 3.12 08/64] ALSA: timer: Fix race among timer ioctls Date: Thu, 11 Feb 2016 14:58:44 +0100 Message-Id: <7210b17187111e20afca4b4e30a31fa13c71a61b.1455198893.git.jslaby@suse.cz> X-Mailer: git-send-email 2.7.1 In-Reply-To: <74c0820133f1dada0d70c74bc70a9530b2697f86.1455198893.git.jslaby@suse.cz> References: <74c0820133f1dada0d70c74bc70a9530b2697f86.1455198893.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Takashi Iwai 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit af368027a49a751d6ff4ee9e3f9961f35bb4fede upstream. ALSA timer ioctls have an open race and this may lead to a use-after-free of timer instance object. A simplistic fix is to make each ioctl exclusive. We have already tread_sem for controlling the tread, and extend this as a global mutex to be applied to each ioctl. The downside is, of course, the worse concurrency. But these ioctls aren't to be parallel accessible, in anyway, so it should be fine to serialize there. Reported-by: Dmitry Vyukov Tested-by: Dmitry Vyukov Signed-off-by: Takashi Iwai Signed-off-by: Jiri Slaby --- sound/core/timer.c | 32 +++++++++++++++++++------------- 1 file changed, 19 insertions(+), 13 deletions(-) diff --git a/sound/core/timer.c b/sound/core/timer.c index 38a137d6b04f..1d5461719e31 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -73,7 +73,7 @@ struct snd_timer_user { struct timespec tstamp; /* trigger tstamp */ wait_queue_head_t qchange_sleep; struct fasync_struct *fasync; - struct mutex tread_sem; + struct mutex ioctl_lock; }; /* list of timers */ @@ -1266,7 +1266,7 @@ static int snd_timer_user_open(struct inode *inode, struct file *file) return -ENOMEM; spin_lock_init(&tu->qlock); init_waitqueue_head(&tu->qchange_sleep); - mutex_init(&tu->tread_sem); + mutex_init(&tu->ioctl_lock); tu->ticks = 1; tu->queue_size = 128; tu->queue = kmalloc(tu->queue_size * sizeof(struct snd_timer_read), @@ -1286,8 +1286,10 @@ static int snd_timer_user_release(struct inode *inode, struct file *file) if (file->private_data) { tu = file->private_data; file->private_data = NULL; + mutex_lock(&tu->ioctl_lock); if (tu->timeri) snd_timer_close(tu->timeri); + mutex_unlock(&tu->ioctl_lock); kfree(tu->queue); kfree(tu->tqueue); kfree(tu); @@ -1525,7 +1527,6 @@ static int snd_timer_user_tselect(struct file *file, int err = 0; tu = file->private_data; - mutex_lock(&tu->tread_sem); if (tu->timeri) { snd_timer_close(tu->timeri); tu->timeri = NULL; @@ -1569,7 +1570,6 @@ static int snd_timer_user_tselect(struct file *file, } __err: - mutex_unlock(&tu->tread_sem); return err; } @@ -1782,7 +1782,7 @@ enum { SNDRV_TIMER_IOCTL_PAUSE_OLD = _IO('T', 0x23), }; -static long snd_timer_user_ioctl(struct file *file, unsigned int cmd, +static long __snd_timer_user_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { struct snd_timer_user *tu; @@ -1799,17 +1799,11 @@ static long snd_timer_user_ioctl(struct file *file, unsigned int cmd, { int xarg; - mutex_lock(&tu->tread_sem); - if (tu->timeri) { /* too late */ - mutex_unlock(&tu->tread_sem); + if (tu->timeri) /* too late */ return -EBUSY; - } - if (get_user(xarg, p)) { - mutex_unlock(&tu->tread_sem); + if (get_user(xarg, p)) return -EFAULT; - } tu->tread = xarg ? 1 : 0; - mutex_unlock(&tu->tread_sem); return 0; } case SNDRV_TIMER_IOCTL_GINFO: @@ -1842,6 +1836,18 @@ static long snd_timer_user_ioctl(struct file *file, unsigned int cmd, return -ENOTTY; } +static long snd_timer_user_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + struct snd_timer_user *tu = file->private_data; + long ret; + + mutex_lock(&tu->ioctl_lock); + ret = __snd_timer_user_ioctl(file, cmd, arg); + mutex_unlock(&tu->ioctl_lock); + return ret; +} + static int snd_timer_user_fasync(int fd, struct file * file, int on) { struct snd_timer_user *tu; -- 2.7.1