[PATCH 3.4 016/172] cdc-acm: add sanity checks

lizf
2015-06-16T08:40:21Z

From: Oliver Neukum <oneukum@suse.de>

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

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

commit 7e860a6e7aa62b337a61110430cd633db5b0d2dd upstream.

Check the special CDC headers for a plausible minimum length.
Another big operating systems ignores such garbage.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Reviewed-by: Adam Lee <adam8157@gmail.com>
Tested-by: Adam Lee <adam8157@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>
---
drivers/usb/class/cdc-acm.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 0532577..57877a9 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -1008,6 +1008,7 @@ static int acm_probe(struct usb_interface *intf,
unsigned long quirks;
int num_rx_buf;
int i;
+ unsigned int elength = 0;
int combined_interfaces = 0;

/* normal quirks */
@@ -1047,9 +1048,12 @@ static int acm_probe(struct usb_interface *intf,
dev_err(&intf->dev, "skipping garbage\n");
goto next_desc;
}
+ elength = buffer[0];

switch (buffer[2]) {
case USB_CDC_UNION_TYPE: /* we've found it */
+ if (elength < sizeof(struct usb_cdc_union_desc))
+ goto next_desc;
if (union_header) {
dev_err(&intf->dev, "More than one "
"union descriptor, skipping ...\n");
@@ -1058,31 +1062,38 @@ static int acm_probe(struct usb_interface *intf,
union_header = (struct usb_cdc_union_desc *)buffer;
break;
case USB_CDC_COUNTRY_TYPE: /* export through sysfs*/
+ if (elength < sizeof(struct usb_cdc_country_functional_desc))
+ goto next_desc;
cfd = (struct usb_cdc_country_functional_desc *)buffer;
break;
case USB_CDC_HEADER_TYPE: /* maybe check version */
break; /* for now we ignore it */
case USB_CDC_ACM_TYPE:
+ if (elength < 4)
+ goto next_desc;
ac_management_function = buffer[3];
break;
case USB_CDC_CALL_MANAGEMENT_TYPE:
+ if (elength < 5)
+ goto next_desc;
call_management_function = buffer[3];
call_interface_num = buffer[4];
if ( (quirks & NOT_A_MODEM) == 0 && (call_management_function & 3) != 3)
dev_err(&intf->dev, "This device cannot do calls on its own. It is not a modem.\n");
break;
default:
- /* there are LOTS more CDC descriptors that
+ /*
+ * there are LOTS more CDC descriptors that
* could legitimately be found here.
*/
dev_dbg(&intf->dev, "Ignoring descriptor: "
- "type %02x, length %d\n",
- buffer[2], buffer[0]);
+ "type %02x, length %ud\n",
+ buffer[2], elength);
break;
}
next_desc:
- buflen -= buffer[0];
- buffer += buffer[0];
+ buflen -= elength;
+ buffer += elength;
}

if (!union_header) {
--
1.9.1