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| author | Takashi Iwai <tiwai@suse.de> | 2024-05-14 20:27:36 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-06-16 13:23:38 +0200 |
| commit | 68396c825c43664b20a3a1ba546844deb2b4e48f (patch) | |
| tree | 78cbddd5ee500b2e28c03f2776aebec39e935d19 | |
| parent | 0049a623dfbbb49888de7f0c2f33a582b5ead989 (diff) | |
| download | linux-stable-68396c825c43664b20a3a1ba546844deb2b4e48f.tar.gz linux-stable-68396c825c43664b20a3a1ba546844deb2b4e48f.tar.bz2 linux-stable-68396c825c43664b20a3a1ba546844deb2b4e48f.zip | |
ALSA: timer: Set lower bound of start tick time
commit 4a63bd179fa8d3fcc44a0d9d71d941ddd62f0c4e upstream.
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>
[ backport note: the error handling is changed, as the original commit
is based on the recent cleanup with guard() in commit beb45974dd49
-- tiwai ]
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | sound/core/timer.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/sound/core/timer.c b/sound/core/timer.c index f0e8b98f346e..d053d70c8d35 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -529,6 +529,16 @@ static int snd_timer_start1(struct snd_timer_instance *timeri, goto unlock; } + /* 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) { + result = -EINVAL; + goto unlock; + } + } + if (start) timeri->ticks = timeri->cticks = ticks; else if (!timeri->cticks) |