ALSA: usb-audio: Fix NULL dereference in create_fixed_stream_quirk()

create_fixed_stream_quirk() may cause a NULL-pointer dereference by
accessing the non-existing endpoint when a USB device with a malformed
USB descriptor is used.

This patch avoids it simply by adding a sanity check of bNumEndpoints
before the accesses.

Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=971125
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 6 insertions, 0 deletions

diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index 5b03296a5bd9..529c35cceaa6 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -180,6 +180,12 @@ static int create_fixed_stream_quirk(struct snd_usb_audio *chip,
         }
         alts = &iface->altsetting[fp->altset_idx];
         altsd = get_iface_desc(alts);
+        if (altsd->bNumEndpoints < 1) {
+                kfree(fp);
+                kfree(rate_table);
+                return -EINVAL;
+        }
+
         fp->protocol = altsd->bInterfaceProtocol;
 
         if (fp->datainterval == 0)