[PATCH 3.18 21/67] ALSA: usb-audio: Add sanity checks to FE parser

[Greg Kroah-Hartman]

3.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Takashi Iwai <ti...@suse.de>

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 <andreyk...@google.com>
Signed-off-by: Takashi Iwai <ti...@suse.de>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 sound/usb/mixer.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1373,6 +1373,12 @@ static int parse_audio_feature_unit(stru
        __u8 *bmaControls;
 
        if (state->mixer->protocol == UAC_VERSION_1) {
+               if (hdr->bLength < 7) {
+                       usb_audio_err(state->chip,
+                                     "unit %u: invalid UAC_FEATURE_UNIT 
descriptor\n",
+                                     unitid);
+                       return -EINVAL;
+               }
                csize = hdr->bControlSize;
                if (!csize) {
                        usb_audio_dbg(state->chip,
@@ -1390,6 +1396,12 @@ static int parse_audio_feature_unit(stru
                }
        } else {
                struct uac2_feature_unit_descriptor *ftr = _ftr;
+               if (hdr->bLength < 6) {
+                       usb_audio_err(state->chip,
+                                     "unit %u: invalid UAC_FEATURE_UNIT 
descriptor\n",
+                                     unitid);
+                       return -EINVAL;
+               }
                csize = 4;
                channels = (hdr->bLength - 6) / 4 - 1;
                bmaControls = ftr->bmaControls;