ALSA: usb-audio: Fix potential out-of-bound access at parsing SU

[ Upstream commit f658f17b5e0e339935dca23e77e0f3cad591926b ]

The usb-audio driver may trigger an out-of-bound access at parsing a
malformed selector unit, as it checks the header length only after
evaluating bNrInPins field, which can be already above the given
length.  Fix it by adding the length check beforehand.

Fixes: 99fc86450c43 ("ALSA: usb-mixer: parse descriptors with structs")
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 9fdec4d7542da5e7315a7124190e628b297162cf..3ebfaa5278253117ff9543942367b18164980175 100644 (file)
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -2020,7 +2020,8 @@ static int parse_audio_selector_unit(struct mixer_build *state, int unitid,
        const struct usbmix_name_map *map;
        char **namelist;
 
-       if (!desc->bNrInPins || desc->bLength < 5 + desc->bNrInPins) {
+       if (desc->bLength < 5 || !desc->bNrInPins ||
+           desc->bLength < 5 + desc->bNrInPins) {
                usb_audio_err(state->chip,
                        "invalid SELECTOR UNIT descriptor %d\n", unitid);
                return -EINVAL;