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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Takashi Iwai" <tiwai@suse.de>,
        "Andrey Konovalov" <andreyknvl@google.com>
Date:   Sun, 11 Feb 2018 04:20:06 +0000
Message-ID: <lsq.1518322806.750552139@decadent.org.uk>
Subject: [PATCH 3.2 55/79] ALSA: usb-audio: Add sanity checks to FE parser
In-Reply-To: <lsq.1518322802.943358572@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.2.99-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Takashi Iwai <tiwai@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 <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>
---
 sound/usb/mixer.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1255,6 +1255,12 @@ static int parse_audio_feature_unit(stru
 	__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(stru
 		}
 	} 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;