[PATCH 4.2.y-ckt 011/218] ALSA: usb-audio: Fix NULL dereference in create_fixed_stream_quirk()

[Kamal Mostafa]

4.2.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Takashi Iwai <tiwai at suse.de>

commit 0f886ca12765d20124bd06291c82951fd49a33be upstream.

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
Signed-off-by: Takashi Iwai <tiwai at suse.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 sound/usb/quirks.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index a4d03e5..47751f0 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -177,6 +177,12 @@ 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)
-- 
2.7.4