Commit 62063644 authored by Takashi Iwai's avatar Takashi Iwai Committed by Jialin Zhang
Browse files

ALSA: pcm: oss: Fix potential out-of-bounds shift 

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=37172cffc6a4e5371c9a514ad6ab870108a73c9f



--------------------------------

commit 175b8d89 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: default avatar <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: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarJialin Zhang <zhangjialin11@huawei.com>
parent 53c51ceb

sound/core/oss/pcm_oss.c

+5 −1
Original line number Diff line number Diff line
@@ -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;