cx231xx-cards: fix NULL-deref at probe

commit 0cd273bb 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: e0d3bafd ("V4L/DVB (10954): Add cx231xx USB driver")

Cc: Sri Deevi <Srinivasa.Deevi@conexant.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/media/usb/cx231xx/cx231xx-cards.c

@@ -1258,6 +1258,9 @@ static int cx231xx_usb_probe(struct usb_interface *interface,
 	uif = udev->actconfig->interface[dev->current_pcb_config.
 		       hs_config_info[0].interface_info.video_index + 1];
 
+	if (uif->altsetting[0].desc.bNumEndpoints < isoc_pipe + 1)
+		return -ENODEV;
+
 	dev->video_mode.end_point_addr = uif->altsetting[0].
 			endpoint[isoc_pipe].desc.bEndpointAddress;
 
@@ -1275,8 +1278,12 @@ static int cx231xx_usb_probe(struct usb_interface *interface,
 	}
 
 	for (i = 0; i < dev->video_mode.num_alt; i++) {
-		u16 tmp = le16_to_cpu(uif->altsetting[i].endpoint[isoc_pipe].
-				desc.wMaxPacketSize);
+		u16 tmp;
+
+		if (uif->altsetting[i].desc.bNumEndpoints < isoc_pipe + 1)
+			return -ENODEV;
+
+		tmp = le16_to_cpu(uif->altsetting[i].endpoint[isoc_pipe].desc.wMaxPacketSize);
 		dev->video_mode.alt_max_pkt_size[i] =
 		    (tmp & 0x07ff) * (((tmp & 0x1800) >> 11) + 1);
 		cx231xx_info("Alternate setting %i, max size= %i\n", i,
@@ -1288,6 +1295,9 @@ static int cx231xx_usb_probe(struct usb_interface *interface,
 				       hs_config_info[0].interface_info.
 				       vanc_index + 1];
 
+	if (uif->altsetting[0].desc.bNumEndpoints < isoc_pipe + 1)
+		return -ENODEV;
+
 	dev->vbi_mode.end_point_addr =
 	    uif->altsetting[0].endpoint[isoc_pipe].desc.
 			bEndpointAddress;
@@ -1306,8 +1316,12 @@ static int cx231xx_usb_probe(struct usb_interface *interface,
 	}
 
 	for (i = 0; i < dev->vbi_mode.num_alt; i++) {
-		u16 tmp =
-		    le16_to_cpu(uif->altsetting[i].endpoint[isoc_pipe].
+		u16 tmp;
+
+		if (uif->altsetting[i].desc.bNumEndpoints < isoc_pipe + 1)
+			return -ENODEV;
+
+		tmp = le16_to_cpu(uif->altsetting[i].endpoint[isoc_pipe].
 				desc.wMaxPacketSize);
 		dev->vbi_mode.alt_max_pkt_size[i] =
 		    (tmp & 0x07ff) * (((tmp & 0x1800) >> 11) + 1);
@@ -1320,6 +1334,9 @@ static int cx231xx_usb_probe(struct usb_interface *interface,
 				       hs_config_info[0].interface_info.
 				       hanc_index + 1];
 
+	if (uif->altsetting[0].desc.bNumEndpoints < isoc_pipe + 1)
+		return -ENODEV;
+
 	dev->sliced_cc_mode.end_point_addr =
 	    uif->altsetting[0].endpoint[isoc_pipe].desc.
 			bEndpointAddress;
@@ -1338,7 +1355,12 @@ static int cx231xx_usb_probe(struct usb_interface *interface,
 	}
 
 	for (i = 0; i < dev->sliced_cc_mode.num_alt; i++) {
-		u16 tmp = le16_to_cpu(uif->altsetting[i].endpoint[isoc_pipe].
+		u16 tmp;
+
+		if (uif->altsetting[i].desc.bNumEndpoints < isoc_pipe + 1)
+			return -ENODEV;
+
+		tmp = le16_to_cpu(uif->altsetting[i].endpoint[isoc_pipe].
 				desc.wMaxPacketSize);
 		dev->sliced_cc_mode.alt_max_pkt_size[i] =
 		    (tmp & 0x07ff) * (((tmp & 0x1800) >> 11) + 1);
@@ -1353,6 +1375,11 @@ static int cx231xx_usb_probe(struct usb_interface *interface,
 					       interface_info.
 					       ts1_index + 1];
 
+		if (uif->altsetting[0].desc.bNumEndpoints < isoc_pipe + 1) {
+			retval = -ENODEV;
+			goto err_video_alt;
+		}
+
 		dev->ts1_mode.end_point_addr =
 		    uif->altsetting[0].endpoint[isoc_pipe].
 				desc.bEndpointAddress;
@@ -1371,7 +1398,14 @@ static int cx231xx_usb_probe(struct usb_interface *interface,
 		}
 
 		for (i = 0; i < dev->ts1_mode.num_alt; i++) {
-			u16 tmp = le16_to_cpu(uif->altsetting[i].
+			u16 tmp;
+
+			if (uif->altsetting[i].desc.bNumEndpoints < isoc_pipe + 1) {
+				retval = -ENODEV;
+				goto err_video_alt;
+			}
+
+			tmp = le16_to_cpu(uif->altsetting[i].
 						endpoint[isoc_pipe].desc.
 						wMaxPacketSize);
 			dev->ts1_mode.alt_max_pkt_size[i] =