diff options
| author | Takashi Iwai <tiwai@suse.de> | 2017-06-02 15:03:38 +0200 |
|---|---|---|
| committer | Mister Oyster <oysterized@gmail.com> | 2017-12-08 17:37:41 +0100 |
| commit | b0d0afd5e6b9ef8da5f74d27b334bc85f36b7593 (patch) | |
| tree | 0cea951d8ce7258bd034a68b08de0d2a25c1195a | |
| parent | 5ccf0686ff68e63fdc76a82b23df05009caa3ec5 (diff) | |
BACKPORT: ALSA: timer: Fix race between read and ioctl
The read from ALSA timer device, the function snd_timer_user_tread(),
may access to an uninitialized struct snd_timer_user fields when the
read is concurrently performed while the ioctl like
snd_timer_user_tselect() is invoked. We have already fixed the races
among ioctls via a mutex, but we seem to have forgotten the race
between read vs ioctl.
This patch simply applies (more exactly extends the already applied
range of) tu->ioctl_lock in snd_timer_user_tread() for closing the
race window.
Reported-by: Alexander Potapenko <glider@google.com>
Tested-by: Alexander Potapenko <glider@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
(cherry picked from commit d11662f4f798b50d8c8743f433842c3e40fe3378)
Signed-off-by: Connor O'Brien <connoro@google.com>
Bug: 62201221
Change-Id: I67a3b5153c39ce9f6d7571b5aa8faabe5e3dbb83
| -rw-r--r-- | sound/core/timer.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/sound/core/timer.c b/sound/core/timer.c index 98904d8e5..a562a4734 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1916,6 +1916,7 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, tu = file->private_data; unit = tu->tread ? sizeof(struct snd_timer_tread) : sizeof(struct snd_timer_read); + mutex_lock(&tu->ioctl_lock); spin_lock_irq(&tu->qlock); while ((long)count - result >= unit) { while (!tu->qused) { @@ -1931,7 +1932,9 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, add_wait_queue(&tu->qchange_sleep, &wait); spin_unlock_irq(&tu->qlock); + mutex_unlock(&tu->ioctl_lock); schedule(); + mutex_lock(&tu->ioctl_lock); spin_lock_irq(&tu->qlock); remove_wait_queue(&tu->qchange_sleep, &wait); @@ -1974,6 +1977,7 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, } spin_unlock_irq(&tu->qlock); _error: + mutex_unlock(&tu->ioctl_lock); return result > 0 ? result : err; } |