diff options
| author | Takashi Iwai <tiwai@suse.de> | 2017-11-05 10:07:43 +0100 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2017-11-06 10:41:24 +0100 |
| commit | 9b7d869ee5a77ed4a462372bb89af622e705bfb8 (patch) | |
| tree | 8151b57ebb526eac4c1bf711aa01bfe0972eecaa /sound/core/hrtimer.c | |
| parent | f5ce817951f38023588b2b8308beca79abe20507 (diff) | |
ALSA: timer: Limit max instances per timer
Currently we allow unlimited number of timer instances, and it may
bring the system hogging way too much CPU when too many timer
instances are opened and processed concurrently. This may end up with
a soft-lockup report as triggered by syzkaller, especially when
hrtimer backend is deployed.
Since such insane number of instances aren't demanded by the normal
use case of ALSA sequencer and it merely opens a risk only for abuse,
this patch introduces the upper limit for the number of instances per
timer backend. As default, it's set to 1000, but for the fine-grained
timer like hrtimer, it's set to 100.
Reported-by: syzbot
Tested-by: Jérôme Glisse <jglisse@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/core/hrtimer.c')
| -rw-r--r-- | sound/core/hrtimer.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/sound/core/hrtimer.c b/sound/core/hrtimer.c index 1ac0c423903e..6e47b823bcaa 100644 --- a/sound/core/hrtimer.c +++ b/sound/core/hrtimer.c @@ -159,6 +159,7 @@ static int __init snd_hrtimer_init(void) timer->hw = hrtimer_hw; timer->hw.resolution = resolution; timer->hw.ticks = NANO_SEC / resolution; + timer->max_instances = 100; /* lower the limit */ err = snd_timer_global_register(timer); if (err < 0) { |