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

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Date:   Mon, 9 Apr 2018 00:35:09 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Takashi Iwai <tiwai@...e.de>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 3.18 001/101] ALSA: timer: Wrap with spinlock for
 queue access

From: Takashi Iwai <tiwai@...e.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 <glider@...gle.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 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