[PATCH 3.2 22/59] [media] cx231xx-audio: fix NULL-deref at probe

[Ben Hutchings]

3.2.92-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Johan Hovold <johan@xxxxxxxxxx>

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.Deevi@xxxxxxxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/media/video/cx231xx/cx231xx-audio.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

--- a/drivers/media/video/cx231xx/cx231xx-audio.c
+++ b/drivers/media/video/cx231xx/cx231xx-audio.c
@@ -680,6 +680,11 @@ 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 =
 	    le16_to_cpu(uif->altsetting[0].endpoint[isoc_pipe].desc.
 			bEndpointAddress);
@@ -695,8 +700,14 @@ 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);
@@ -706,6 +717,8 @@ 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);