USB: serial: visor: handle potential invalid device configuration

BugLink: http://bugs.launchpad.net/bugs/1778759
commit 4842ed5bfcb9daf6660537d70503c18d38dbdbb8 upstream.

If we get an invalid device configuration from a palm 3 type device, we
might incorrectly parse things, and we have the potential to crash in
"interesting" ways.

Fix this up by verifying the size of the configuration passed to us by
the device, and only if it is correct, will we handle it.

Note that this also fixes an information leak of slab data.

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ johan: add comment about the info leak ]
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/usb/serial/visor.c b/drivers/usb/serial/visor.c
index f5373ed2cd455dbb0e58fa81aba7338b6fbf22f0..8ddbecc25d89ac6fbb2bc1a385b569d00f2737b2 100644 (file)
--- a/drivers/usb/serial/visor.c
+++ b/drivers/usb/serial/visor.c
@@ -335,47 +335,48 @@ static int palm_os_3_probe(struct usb_serial *serial,
                goto exit;
        }
 
-       if (retval == sizeof(*connection_info)) {
-                       connection_info = (struct visor_connection_info *)
-                                                       transfer_buffer;
-
-               num_ports = le16_to_cpu(connection_info->num_ports);
-               for (i = 0; i < num_ports; ++i) {
-                       switch (
-                          connection_info->connections[i].port_function_id) {
-                       case VISOR_FUNCTION_GENERIC:
-                               string = "Generic";
-                               break;
-                       case VISOR_FUNCTION_DEBUGGER:
-                               string = "Debugger";
-                               break;
-                       case VISOR_FUNCTION_HOTSYNC:
-                               string = "HotSync";
-                               break;
-                       case VISOR_FUNCTION_CONSOLE:
-                               string = "Console";
-                               break;
-                       case VISOR_FUNCTION_REMOTE_FILE_SYS:
-                               string = "Remote File System";
-                               break;
-                       default:
-                               string = "unknown";
-                               break;
-                       }
-                       dev_info(dev, "%s: port %d, is for %s use\n",
-                               serial->type->description,
-                               connection_info->connections[i].port, string);
-               }
+       if (retval != sizeof(*connection_info)) {
+               dev_err(dev, "Invalid connection information received from device\n");
+               retval = -ENODEV;
+               goto exit;
        }
-       /*
-       * Handle devices that report invalid stuff here.
-       */
+
+       connection_info = (struct visor_connection_info *)transfer_buffer;
+
+       num_ports = le16_to_cpu(connection_info->num_ports);
+
+       /* Handle devices that report invalid stuff here. */
        if (num_ports == 0 || num_ports > 2) {
                dev_warn(dev, "%s: No valid connect info available\n",
                        serial->type->description);
                num_ports = 2;
        }
 
+       for (i = 0; i < num_ports; ++i) {
+               switch (connection_info->connections[i].port_function_id) {
+               case VISOR_FUNCTION_GENERIC:
+                       string = "Generic";
+                       break;
+               case VISOR_FUNCTION_DEBUGGER:
+                       string = "Debugger";
+                       break;
+               case VISOR_FUNCTION_HOTSYNC:
+                       string = "HotSync";
+                       break;
+               case VISOR_FUNCTION_CONSOLE:
+                       string = "Console";
+                       break;
+               case VISOR_FUNCTION_REMOTE_FILE_SYS:
+                       string = "Remote File System";
+                       break;
+               default:
+                       string = "unknown";
+                       break;
+               }
+               dev_info(dev, "%s: port %d, is for %s use\n",
+                       serial->type->description,
+                       connection_info->connections[i].port, string);
+       }
        dev_info(dev, "%s: Number of ports: %d\n", serial->type->description,
                num_ports);