ALSA: timer: Fix link corruption due to double start or stop

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commit f784beb75c upstream.

Although ALSA timer code got hardening for races, it still causes
use-after-free error.  This is however rather a corrupted linked list,
not actually the concurrent accesses.  Namely, when timer start is
triggered twice, list_add_tail() is called twice, too.  This ends
up with the link corruption and triggers KASAN error.

The simplest fix would be replacing list_add_tail() with
list_move_tail(), but fundamentally it's the problem that we don't
check the double start/stop correctly.  So, the right fix here is to
add the proper checks to snd_timer_start() and snd_timer_stop() (and
their variants).

BugLink: http://lkml.kernel.org/r/CACT4Y+ZyPRoMQjmawbvmCEDrkBD2BQuH7R09=eOkf5ESK8kJAw@mail.gmail.com
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

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Takashi Iwai 2016-01-30 23:09:08 +01:00 • committed by Luis Henriques

parent a293ce87a6

commit 95cd42a480

1 changed files with 28 additions and 2 deletions

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sound/core/timer.c

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