[PATCH AUTOSEL for 4.9 001/293] ALSA: timer: Wrap with spinlock for queue access

[Sasha Levin]

From: Takashi Iwai <ti...@suse.de>

[ Upstream commit d7f910bfedd863d13ea320030fe98e42d0938ed5 ]

For accessing the snd_timer_user queue indices, we take tu->qlock.
But it's forgotten in a couple of places.

The one in snd_timer_user_params() should be safe without the
spinlock as the timer is already stopped.  But it's better for
consistency.

The one in poll is just a read-out, so it's not inevitably needed, but
it'd be good to make the result consistent, too.

Tested-by: Alexander Potapenko <gli...@google.com>
Signed-off-by: Takashi Iwai <ti...@suse.de>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 sound/core/timer.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sound/core/timer.c b/sound/core/timer.c
index e5ddc475dca4..bbde1bcdd985 100644
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -1773,6 +1773,7 @@ static int snd_timer_user_params(struct file *file,
                        }
                }
        }
+       spin_lock_irq(&tu->qlock);
        tu->qhead = tu->qtail = tu->qused = 0;
        if (tu->timeri->flags & SNDRV_TIMER_IFLG_EARLY_EVENT) {
                if (tu->tread) {
@@ -1793,6 +1794,7 @@ static int snd_timer_user_params(struct file *file,
        }
        tu->filter = params.filter;
        tu->ticks = params.ticks;
+       spin_unlock_irq(&tu->qlock);
        err = 0;
  _end:
        if (copy_to_user(_params, &params, sizeof(params)))
@@ -2034,10 +2036,12 @@ static unsigned int snd_timer_user_poll(struct file 
*file, poll_table * wait)
         poll_wait(file, &tu->qchange_sleep, wait);
 
        mask = 0;
+       spin_lock_irq(&tu->qlock);
        if (tu->qused)
                mask |= POLLIN | POLLRDNORM;
        if (tu->disconnected)
                mask |= POLLERR;
+       spin_unlock_irq(&tu->qlock);
 
        return mask;
 }
-- 
2.15.1