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| author | Takashi Iwai <tiwai@suse.de> | 2024-05-14 20:27:36 +0200 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2024-05-16 16:00:08 +0200 |
| commit | 4a63bd179fa8d3fcc44a0d9d71d941ddd62f0c4e (patch) | |
| tree | bcad0f5fa5268550dad3f171fd1790921c5b68ac /sound | |
| parent | d731b1ed15052580b7b2f40559021012d280f1d9 (diff) | |
| download | lwn-4a63bd179fa8d3fcc44a0d9d71d941ddd62f0c4e.tar.gz lwn-4a63bd179fa8d3fcc44a0d9d71d941ddd62f0c4e.zip | |
ALSA: timer: Set lower bound of start tick time
Currently ALSA timer doesn't have the lower limit of the start tick
time, and it allows a very small size, e.g. 1 tick with 1ns resolution
for hrtimer. Such a situation may lead to an unexpected RCU stall,
where the callback repeatedly queuing the expire update, as reported
by fuzzer.
This patch introduces a sanity check of the timer start tick time, so
that the system returns an error when a too small start size is set.
As of this patch, the lower limit is hard-coded to 100us, which is
small enough but can still work somehow.
Reported-by: syzbot+43120c2af6ca2938cc38@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/r/000000000000fa00a1061740ab6d@google.com
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20240514182745.4015-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound')
| -rw-r--r-- | sound/core/timer.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/sound/core/timer.c b/sound/core/timer.c index 4d2ee99c12a3..d104adc75a8b 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -544,6 +544,14 @@ static int snd_timer_start1(struct snd_timer_instance *timeri, SNDRV_TIMER_IFLG_START)) return -EBUSY; + /* check the actual time for the start tick; + * bail out as error if it's way too low (< 100us) + */ + if (start) { + if ((u64)snd_timer_hw_resolution(timer) * ticks < 100000) + return -EINVAL; + } + if (start) timeri->ticks = timeri->cticks = ticks; else if (!timeri->cticks) |