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ALSA: timer: Fix leftover link at closing 

In ALSA timer core, the active timer instance is managed in
active_list linked list.  Each element is added / removed dynamically
at timer start, stop and in timer interrupt.  The problem is that
snd_timer_interrupt() has a thinko and leaves the element in
active_list when it's the last opened element.  This eventually leads
to list corruption or use-after-free error.

This hasn't been revealed because we used to delete the list forcibly
in snd_timer_stop() in the past.  However, the recent fix avoids the
double-stop behavior (in commit [f784beb75ce8: ALSA: timer: Fix link
corruption due to double start or stop]), and this leak hits reality.

This patch fixes the link management in snd_timer_interrupt().  Now it
simply unlinks no matter which stream is.

BugLink: http://lkml.kernel.org/r/CACT4Y+Yy2aukHP-EDp8-ziNqNNmb-NTf=jDWXMP7jB8HDa2vng@mail.gmail.com
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
steinar/wifi_calib_4_9_kernel
Takashi Iwai 2016-02-04 17:06:13 +01:00
parent 2e5dc73fe1
commit 094fd3be87
1 changed files with 2 additions and 2 deletions
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4
sound/core/timer.c
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@ -744,8 +744,8 @@ void snd_timer_interrupt(struct snd_timer * timer, unsigned long ticks_left)
ti->cticks = ti->ticks;
} else {
ti->flags &= ~SNDRV_TIMER_IFLG_RUNNING;
if (--timer->running)
list_del_init(&ti->active_list);
--timer->running;
list_del_init(&ti->active_list);
}
if ((timer->hw.flags & SNDRV_TIMER_HW_TASKLET) ||
(ti->flags & SNDRV_TIMER_IFLG_FAST))