[PATCH 1/2] ALSA: usb-audio: Fix potential out-of-bounds shift

[PATCH 1/2] ALSA: usb-audio: Fix potential out-of-bounds shift

[Takashi Iwai]

syzbot spotted a potential out-of-bounds shift in the USB-audio format
parser that receives the arbitrary shift value from the USB
descriptor.

Add a range check for avoiding the undefined behavior.

Reported-by: syzbot+df7dc146ebdd6435eea3@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/usb/format.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sound/usb/format.c b/sound/usb/format.c
index 93459ba228d3..9ebc5d202c87 100644
--- a/sound/usb/format.c
+++ b/sound/usb/format.c
@@ -39,6 +39,8 @@ static u64 parse_audio_format_i_type(struct snd_usb_audio *chip,
 	case UAC_VERSION_1:
 	default: {
 		struct uac_format_type_i_discrete_descriptor *fmt = _fmt;
+		if (format >= 64)
+			return 0; /* invalid format */
 		sample_width = fmt->bBitResolution;
 		sample_bytes = fmt->bSubframeSize;
 		format = 1ULL << format;
-- 
2.26.2

[PATCH 2/2] ALSA: pcm: oss: Fix potential out-of-bounds shift

[Takashi Iwai]

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>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 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 327ec42a36b0..de1917484647 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -1935,11 +1935,15 @@ 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;
-- 
2.26.2