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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Takashi Iwai <tiwai@suse.de>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 001/293] ALSA: timer: Wrap with spinlock for
 queue access
Thread-Topic: [PATCH AUTOSEL for 4.9 001/293] ALSA: timer: Wrap with spinlock
 for queue access
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Date:   Mon, 9 Apr 2018 00:22:45 +0000
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From: Takashi Iwai <tiwai@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 <glider@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <alexander.levin@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 =3D tu->qtail =3D tu->qused =3D 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 =3D params.filter;
 	tu->ticks =3D params.ticks;
+	spin_unlock_irq(&tu->qlock);
 	err =3D 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);
=20
 	mask =3D 0;
+	spin_lock_irq(&tu->qlock);
 	if (tu->qused)
 		mask |=3D POLLIN | POLLRDNORM;
 	if (tu->disconnected)
 		mask |=3D POLLERR;
+	spin_unlock_irq(&tu->qlock);
=20
 	return mask;
 }
--=20
2.15.1