CVE-2020-11609 (published 2020-04-07T17:15Z)

An issue was discovered in the stv06xx subsystem in the Linux kernel before 5.6.1. drivers/media/usb/gspca/stv06xx/stv06xx.c and drivers/media/usb/gspca/stv06xx/stv06xx_pb0100.c mishandle invalid descriptors, as demonstrated by a NULL pointer dereference, aka CID-485b06aadb93.

Severity: MEDIUM
CVSS v2 base score: 4.9 (AV:L/AC:L/Au:N/C:N/I:N/A:C)
CVSS v3 base score: 4.3, MEDIUM (CVSS:3.1/AV:P/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)

Weakness information:
cwe_id: CWE-476
cwe_name: NULL Pointer Dereference
description: The product dereferences a pointer that it expects to be valid but is NULL.
extended_description: 
            
            
            
         
         

Fix information:
repo_url: https://github.com/torvalds/linux
commit_details: repo_url: https://github.com/torvalds/linux
author: Johan Hovold
author_date: 2020-01-03 17:35:10+01:00
msg: media: stv06xx: add missing descriptor sanity checks

Make sure to check that we have two alternate settings and at least one
endpoint before accessing the second altsetting structure and
dereferencing the endpoint arrays.

This specifically avoids dereferencing NULL-pointers or corrupting
memory when a device does not have the expected descriptors.

Note that the sanity checks in stv06xx_start() and pb0100_start() are
not redundant as the driver is mixing looking up altsettings by index
and by number, which may not coincide.

Fixes: 8668d504d72c ("V4L/DVB (12082): gspca_stv06xx: Add support for st6422 bridge and sensor")
Fixes: c0b33bdc5b8d ("[media] gspca-stv06xx: support bandwidth changing")
Cc: stable <stable@vger.kernel.org>     # 2.6.31
Cc: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
repository: repo_url: https://github.com/torvalds/linux
repo_name: torvalds/linux
description: Linux kernel source tree
repo_language: C
owner: torvalds
file_changes: filename: stv06xx.c
change_type: ModificationType.MODIFY
diff: @@ -282,6 +282,9 @@ static int stv06xx_start(struct gspca_dev *gspca_dev)
 		return -EIO;
 	}
 
+	if (alt->desc.bNumEndpoints < 1)
+		return -ENODEV;
+
 	packet_size = le16_to_cpu(alt->endpoint[0].desc.wMaxPacketSize);
 	err = stv06xx_write_bridge(sd, STV_ISO_SIZE_L, packet_size);
 	if (err < 0)
@@ -306,11 +309,21 @@ static int stv06xx_start(struct gspca_dev *gspca_dev)
 
 static int stv06xx_isoc_init(struct gspca_dev *gspca_dev)
 {
+	struct usb_interface_cache *intfc;
 	struct usb_host_interface *alt;
 	struct sd *sd = (struct sd *) gspca_dev;
 
+	intfc = gspca_dev->dev->actconfig->intf_cache[0];
+
+	if (intfc->num_altsetting < 2)
+		return -ENODEV;
+
+	alt = &intfc->altsetting[1];
+
+	if (alt->desc.bNumEndpoints < 1)
+		return -ENODEV;
+
 	/* Start isoc bandwidth "negotiation" at max isoc bandwidth */
-	alt = &gspca_dev->dev->actconfig->intf_cache[0]->altsetting[1];
 	alt->endpoint[0].desc.wMaxPacketSize =
 		cpu_to_le16(sd->sensor->max_packet_size[gspca_dev->curr_mode]);
 
@@ -323,6 +336,10 @@ static int stv06xx_isoc_nego(struct gspca_dev *gspca_dev)
 	struct usb_host_interface *alt;
 	struct sd *sd = (struct sd *) gspca_dev;
 
+	/*
+	 * Existence of altsetting and endpoint was verified in
+	 * stv06xx_isoc_init()
+	 */
 	alt = &gspca_dev->dev->actconfig->intf_cache[0]->altsetting[1];
 	packet_size = le16_to_cpu(alt->endpoint[0].desc.wMaxPacketSize);
 	min_packet_size = sd->sensor->min_packet_size[gspca_dev->curr_mode];

programming_language: C
filename: stv06xx_pb0100.c
change_type: ModificationType.MODIFY
diff: @@ -185,6 +185,10 @@ static int pb0100_start(struct sd *sd)
 	alt = usb_altnum_to_altsetting(intf, sd->gspca_dev.alt);
 	if (!alt)
 		return -ENODEV;
+
+	if (alt->desc.bNumEndpoints < 1)
+		return -ENODEV;
+
 	packet_size = le16_to_cpu(alt->endpoint[0].desc.wMaxPacketSize);
 
 	/* If we don't have enough bandwidth use a lower framerate */

programming_language: C