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authorTakashi Iwai <tiwai@suse.de>2016-01-13 17:48:01 +0100
committerTakashi Iwai <tiwai@suse.de>2016-01-14 14:07:21 +0100
commitaf368027a49a751d6ff4ee9e3f9961f35bb4fede (patch)
treeca51f654c1b2f2d660a211b2a21dacc57f36cb62
parent91815d8aa7e2f45d30e51caa297061ad893628d9 (diff)
ALSA: timer: Fix race among timer ioctls
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 <dvyukov@google.com> Tested-by: Dmitry Vyukov <dvyukov@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
-rw-r--r--sound/core/timer.c32
1 files changed, 19 insertions, 13 deletions
diff --git a/sound/core/timer.c b/sound/core/timer.c
index 9241784df..3810ee8 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 */
@@ -1253,7 +1253,7 @@ 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),
@@ -1273,8 +1273,10 @@ 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);
@@ -1512,7 +1514,6 @@ 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;
@@ -1556,7 +1557,6 @@ static int snd_timer_user_tselect(struct file *file,
}
__err:
- mutex_unlock(&tu->tread_sem);
return err;
}
@@ -1769,7 +1769,7 @@ 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;
@@ -1786,17 +1786,11 @@ 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:
@@ -1829,6 +1823,18 @@ 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;