ALSA: usb-audio: Add sanity checks to FE parser

commit d937cd6790a2bef2d07b500487646bd794c039bb upstream.

When the usb-audio descriptor contains the malformed feature unit
description with a too short length, the driver may access
out-of-bounds.  Add a sanity check of the header size at the beginning
of parse_audio_feature_unit().

Fixes: 23caaf19b11e ("ALSA: usb-mixer: Add support for Audio Class v2.0")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[bwh: Backported to 3.2: use snd_printk() for logging]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index a489f2f..457cf8b 100644 (file)
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1255,6 +1255,12 @@ static int parse_audio_feature_unit(struct mixer_build *state, int unitid, void
        __u8 *bmaControls;
 
        if (state->mixer->protocol == UAC_VERSION_1) {
+               if (hdr->bLength < 7) {
+                       snd_printk(KERN_ERR
+                                  "usbaudio: unit %u: invalid UAC_FEATURE_UNIT descriptor\n",
+                                  unitid);
+                       return -EINVAL;
+               }
                csize = hdr->bControlSize;
                if (!csize) {
                        snd_printdd(KERN_ERR "usbaudio: unit %u: "
@@ -1271,6 +1277,12 @@ static int parse_audio_feature_unit(struct mixer_build *state, int unitid, void
                }
        } else {
                struct uac2_feature_unit_descriptor *ftr = _ftr;
+               if (hdr->bLength < 6) {
+                       snd_printk(KERN_ERR
+                                  "usbaudio: unit %u: invalid UAC_FEATURE_UNIT descriptor\n",
+                                  unitid);
+                       return -EINVAL;
+               }
                csize = 4;
                channels = (hdr->bLength - 6) / 4 - 1;
                bmaControls = ftr->bmaControls;