| Message ID | 20240514182745.4015-1-tiwai@suse.de (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 4a63bd179fa8d3fcc44a0d9d71d941ddd62f0c4e |
| Headers | show |
| Series | ALSA: timer: Set lower bound of start tick time | expand |
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)
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> Signed-off-by: Takashi Iwai <tiwai@suse.de> --- sound/core/timer.c | 8 ++++++++ 1 file changed, 8 insertions(+)