[PATCH AUTOSEL for 3.18 001/101] ALSA: timer: Wrap with spinlock for queue access

From: Sasha Levin
Date: Sun Apr 08 2018 - 21:00:22 EST


From: Takashi Iwai <tiwai@xxxxxxx>

[ 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 <glider@xxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
sound/core/timer.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/sound/core/timer.c b/sound/core/timer.c
index 6e01a8e3e4ae..c4e4b2925868 100644
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -1758,6 +1758,7 @@ 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) {
@@ -1778,6 +1779,7 @@ 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)))
@@ -2019,10 +2021,12 @@ 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