[PATCH 4.4 077/103] [media] cx231xx-audio: fix NULL-deref at probe

[Greg Kroah-Hartman]

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

------------------

From: Johan Hovold <jo...@kernel.org>

commit 65f921647f4c89a2068478c89691f39b309b58f7 upstream.

Make sure to check the number of endpoints to avoid dereferencing a
NULL-pointer or accessing memory beyond the endpoint array should a
malicious device lack the expected endpoints.

Fixes: e0d3bafd0258 ("V4L/DVB (10954): Add cx231xx USB driver")

Cc: Sri Deevi <srinivasa.de...@conexant.com>
Signed-off-by: Johan Hovold <jo...@kernel.org>
Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mche...@s-opensource.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/media/usb/cx231xx/cx231xx-audio.c |   17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

--- a/drivers/media/usb/cx231xx/cx231xx-audio.c
+++ b/drivers/media/usb/cx231xx/cx231xx-audio.c
@@ -698,6 +698,11 @@ static int cx231xx_audio_init(struct cx2
                                            hs_config_info[0].interface_info.
                                            audio_index + 1];
 
+       if (uif->altsetting[0].desc.bNumEndpoints < isoc_pipe + 1) {
+               err = -ENODEV;
+               goto err_free_card;
+       }
+
        adev->end_point_addr =
            uif->altsetting[0].endpoint[isoc_pipe].desc.
                        bEndpointAddress;
@@ -713,8 +718,14 @@ static int cx231xx_audio_init(struct cx2
        }
 
        for (i = 0; i < adev->num_alt; i++) {
-               u16 tmp =
-                   le16_to_cpu(uif->altsetting[i].endpoint[isoc_pipe].desc.
+               u16 tmp;
+
+               if (uif->altsetting[i].desc.bNumEndpoints < isoc_pipe + 1) {
+                       err = -ENODEV;
+                       goto err_free_pkt_size;
+               }
+
+               tmp = le16_to_cpu(uif->altsetting[i].endpoint[isoc_pipe].desc.
                                wMaxPacketSize);
                adev->alt_max_pkt_size[i] =
                    (tmp & 0x07ff) * (((tmp & 0x1800) >> 11) + 1);
@@ -725,6 +736,8 @@ static int cx231xx_audio_init(struct cx2
 
        return 0;
 
+err_free_pkt_size:
+       kfree(adev->alt_max_pkt_size);
 err_free_card:
        snd_card_free(card);