diff options
| author | Takashi Iwai <tiwai@suse.de> | 2016-07-04 14:02:15 +0200 |
|---|---|---|
| committer | Sasha Levin <alexander.levin@verizon.com> | 2016-07-19 13:58:06 -0400 |
| commit | 1dd148a1b9beb04150bbd6deae2518b73bbe937c (patch) | |
| tree | 41fbfe8ca1b195534f14d304afd75ffed5a7f5e8 | |
| parent | 23c63b8c08fe3f0b21594ee1ac4de0fa52225f79 (diff) | |
ALSA: timer: Fix negative queue usage by racy accesses
[ Upstream commit 3fa6993fef634e05d200d141a85df0b044572364 ]
The user timer tu->qused counter may go to a negative value when
multiple concurrent reads are performed since both the check and the
decrement of tu->qused are done in two individual locked contexts.
This results in bogus read outs, and the endless loop in the
user-space side.
The fix is to move the decrement of the tu->qused counter into the
same spinlock context as the zero-check of the counter.
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
| -rw-r--r-- | sound/core/timer.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/sound/core/timer.c b/sound/core/timer.c index 1782555fcaca..7e3020c1e9d3 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1961,6 +1961,7 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, qhead = tu->qhead++; tu->qhead %= tu->queue_size; + tu->qused--; spin_unlock_irq(&tu->qlock); if (tu->tread) { @@ -1974,7 +1975,6 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, } spin_lock_irq(&tu->qlock); - tu->qused--; if (err < 0) goto _error; result += unit; |