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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,
        "Andrey Konovalov" <andreyknvl@google.com>,
        "Takashi Iwai" <tiwai@suse.de>
Date:   Sun, 11 Feb 2018 04:20:06 +0000
Message-ID: <lsq.1518322806.886964410@decadent.org.uk>
Subject: [PATCH 3.2 58/79] ALSA: usb-audio: Add sanity checks in v2 clock
 parsers
In-Reply-To: <lsq.1518322802.943358572@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

3.2.99-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Takashi Iwai <tiwai@suse.de>

commit 0a62d6c966956d77397c32836a5bbfe3af786fc1 upstream.

The helper functions to parse and look for the clock source, selector
and multiplier unit may return the descriptor with a too short length
than required, while there is no sanity check in the caller side.
Add some sanity checks in the parsers, at least, to guarantee the
given descriptor size, for avoiding the potential crashes.

Fixes: 79f920fbff56 ("ALSA: usb-audio: parse clock topology of UAC2 devices")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 sound/usb/clock.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/sound/usb/clock.c
+++ b/sound/usb/clock.c
@@ -42,7 +42,7 @@ static struct uac_clock_source_descripto
 	while ((cs = snd_usb_find_csint_desc(ctrl_iface->extra,
 					     ctrl_iface->extralen,
 					     cs, UAC2_CLOCK_SOURCE))) {
-		if (cs->bClockID == clock_id)
+		if (cs->bLength >= sizeof(*cs) && cs->bClockID == clock_id)
 			return cs;
 	}
 
@@ -58,8 +58,11 @@ static struct uac_clock_selector_descrip
 	while ((cs = snd_usb_find_csint_desc(ctrl_iface->extra,
 					     ctrl_iface->extralen,
 					     cs, UAC2_CLOCK_SELECTOR))) {
-		if (cs->bClockID == clock_id)
+		if (cs->bLength >= sizeof(*cs) && cs->bClockID == clock_id) {
+			if (cs->bLength < 5 + cs->bNrInPins)
+				return NULL;
 			return cs;
+		}
 	}
 
 	return NULL;
@@ -74,7 +77,7 @@ static struct uac_clock_multiplier_descr
 	while ((cs = snd_usb_find_csint_desc(ctrl_iface->extra,
 					     ctrl_iface->extralen,
 					     cs, UAC2_CLOCK_MULTIPLIER))) {
-		if (cs->bClockID == clock_id)
+		if (cs->bLength >= sizeof(*cs) && cs->bClockID == clock_id)
 			return cs;
 	}