USB: hso: Fix OOB memory access in hso_probe/hso_get_config_data

The function hso_probe reads if_num from the USB device (as an u8) and uses
it without a length check to index an array, resulting in an OOB memory read
in hso_probe or hso_get_config_data.

Add a length check for both locations and updated hso_probe to bail on
error.

This issue has been assigned CVE-2018-19985.

Reported-by: Hui Peng <benquike@gmail.com>
Reported-by: Mathias Payer <mathias.payer@nebelwelt.net>
Signed-off-by: Hui Peng <benquike@gmail.com>
Signed-off-by: Mathias Payer <mathias.payer@nebelwelt.net>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index 184c24baca1527333d92ec927c48e958ad6c95f0..d6916f787fce98ae2ce4d51d0619eb5094738543 100644 (file)
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -2807,6 +2807,12 @@ static int hso_get_config_data(struct usb_interface *interface)
                return -EIO;
        }
 
+       /* check if we have a valid interface */
+       if (if_num > 16) {
+               kfree(config_data);
+               return -EINVAL;
+       }
+
        switch (config_data[if_num]) {
        case 0x0:
                result = 0;
@@ -2877,10 +2883,18 @@ static int hso_probe(struct usb_interface *interface,
 
        /* Get the interface/port specification from either driver_info or from
         * the device itself */
-       if (id->driver_info)
+       if (id->driver_info) {
+               /* if_num is controlled by the device, driver_info is a 0 terminated
+                * array. Make sure, the access is in bounds! */
+               for (i = 0; i <= if_num; ++i)
+                       if (((u32 *)(id->driver_info))[i] == 0)
+                               goto exit;
                port_spec = ((u32 *)(id->driver_info))[if_num];
-       else
+       } else {
                port_spec = hso_get_config_data(interface);
+               if (port_spec < 0)
+                       goto exit;
+       }
 
        /* Check if we need to switch to alt interfaces prior to port
         * configuration */