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

commit f658f17b5e0e339935dca23e77e0f3cad591926b upstream.

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")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index a6921d8b19a306de4849dcc445fcc120d7407e1e..9133d3e53d9d64faa5b884078d00cc497317d694 100644 (file)
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -2092,7 +2092,8 @@ 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;