From: Takashi Iwai tiwai@suse.de

stable inclusion from stable-v4.19.164 commit 37172cffc6a4e5371c9a514ad6ab870108a73c9f category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9S1ZV CVE: CVE-2021-47509

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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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 Signed-off-by: Jialin Zhang zhangjialin11@huawei.com --- sound/core/oss/pcm_oss.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c index b41962e78a88..6baf50f4def3 100644 --- a/sound/core/oss/pcm_oss.c +++ b/sound/core/oss/pcm_oss.c @@ -1962,11 +1962,15 @@ static int snd_pcm_oss_set_subdivide(struct snd_pcm_oss_file *pcm_oss_file, int 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;