From: Takashi Iwai tiwai@suse.de
commit 175b8d89fe292796811fdee87fa39799a5b6b87a upstream.
syzbot spotted a potential out-of-bounds shift in the PCM OSS layer where it calculates the buffer size with the arbitrary shift value given via an ioctl.
Add a range check for avoiding the undefined behavior. As the value can be treated by a signed integer, the max shift should be 30.
Reported-by: syzbot+df7dc146ebdd6435eea3@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201209084552.17109-2-tiwai@suse.de Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- sound/core/oss/pcm_oss.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/sound/core/oss/pcm_oss.c +++ b/sound/core/oss/pcm_oss.c @@ -2000,11 +2000,15 @@ static int snd_pcm_oss_set_subdivide(str static int snd_pcm_oss_set_fragment1(struct snd_pcm_substream *substream, unsigned int val) { struct snd_pcm_runtime *runtime; + int fragshift;
runtime = substream->runtime; if (runtime->oss.subdivision || runtime->oss.fragshift) return -EINVAL; - runtime->oss.fragshift = val & 0xffff; + fragshift = val & 0xffff; + if (fragshift >= 31) + return -EINVAL; + runtime->oss.fragshift = fragshift; runtime->oss.maxfrags = (val >> 16) & 0xffff; if (runtime->oss.fragshift < 4) /* < 16 */ runtime->oss.fragshift = 4;