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author | Takashi Iwai <tiwai@suse.de> | 2016-01-14 16:30:58 +0100 |
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committer | Takashi Iwai <tiwai@suse.de> | 2016-01-15 15:50:34 +0100 |
commit | b5a663aa426f4884c71cd8580adae73f33570f0d (patch) | |
tree | 87f6d8a3994ca42949130ddb53cb51603fea704f /Documentation | |
parent | cf52103a218744f3fd18111325c28e95aa9cd226 (diff) |
ALSA: timer: Harden slave timer list handling
A slave timer instance might be still accessible in a racy way while
operating the master instance as it lacks of locking. Since the
master operation is mostly protected with timer->lock, we should cope
with it while changing the slave instance, too. Also, some linked
lists (active_list and ack_list) of slave instances aren't unlinked
immediately at stopping or closing, and this may lead to unexpected
accesses.
This patch tries to address these issues. It adds spin lock of
timer->lock (either from master or slave, which is equivalent) in a
few places. For avoiding a deadlock, we ensure that the global
slave_active_lock is always locked at first before each timer lock.
Also, ack and active_list of slave instances are properly unlinked at
snd_timer_stop() and snd_timer_close().
Last but not least, remove the superfluous call of _snd_timer_stop()
at removing slave links. This is a noop, and calling it may confuse
readers wrt locking. Further cleanup will follow in a later patch.
Actually we've got reports of use-after-free by syzkaller fuzzer, and
this hopefully fixes these issues.
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'Documentation')
0 files changed, 0 insertions, 0 deletions