From 0a62d6c966956d77397c32836a5bbfe3af786fc1 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Tue, 21 Nov 2017 17:28:06 +0100
Subject: [PATCH] ALSA: usb-audio: Add sanity checks in v2 clock parsers
Patch-mainline: v4.15-rc1
References: bsc#1051510
Git-commit: 0a62d6c966956d77397c32836a5bbfe3af786fc1

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/usb/clock.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/sound/usb/clock.c
+++ b/sound/usb/clock.c
@@ -43,7 +43,7 @@ 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;
 	}
 
@@ -59,8 +59,11 @@ 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;
@@ -75,7 +78,7 @@ 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;
 	}