diff options
| author | Takashi Iwai <tiwai@suse.de> | 2017-06-02 15:03:38 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-06-14 12:54:21 +0200 |
| commit | d96c363ff004fbb42f728b3e4299a71c4e567568 (patch) | |
| tree | dc0735c10d6095158de72f467e77b8a1a9f32d3f | |
| parent | 4489545a1d45d1163f7c6eb83a6c38ee5082d1f5 (diff) | |
ALSA: timer: Fix race between read and ioctl
commit d11662f4f798b50d8c8743f433842c3e40fe3378 upstream.
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>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -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 2779728127d2..6e01a8e3e4ae 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1949,6 +1949,7 @@ 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) { @@ -1964,7 +1965,9 @@ 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); @@ -2002,6 +2005,7 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, } _error: spin_unlock_irq(&tu->qlock); + mutex_unlock(&tu->ioctl_lock); return result > 0 ? result : err; } |