USB: fix out-of-bounds in usb_set_configuration

commit bd7a3fe770ebd8391d1c7d072ff88e9e76d063eb upstream.

Andrey Konovalov reported a possible out-of-bounds problem for a USB interface
association descriptor.  He writes:
	It seems there's no proper size check of a USB_DT_INTERFACE_ASSOCIATION
	descriptor. It's only checked that the size is >= 2 in
	usb_parse_configuration(), so find_iad() might do out-of-bounds access
	to intf_assoc->bInterfaceCount.

And he's right, we don't check for crazy descriptors of this type very well, so
resolve this problem.  Yet another issue found by syzkaller...

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index 5dc08c7..1179338 100644 (file)
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -638,15 +638,23 @@ static int usb_parse_configuration(struct usb_device *dev, int cfgidx,
 
                } else if (header->bDescriptorType ==
                                USB_DT_INTERFACE_ASSOCIATION) {
+                       struct usb_interface_assoc_descriptor *d;
+
+                       d = (struct usb_interface_assoc_descriptor *)header;
+                       if (d->bLength < USB_DT_INTERFACE_ASSOCIATION_SIZE) {
+                               dev_warn(ddev,
+                                        "config %d has an invalid interface association descriptor of length %d, skipping\n",
+                                        cfgno, d->bLength);
+                               continue;
+                       }
+
                        if (iad_num == USB_MAXIADS) {
                                dev_warn(ddev, "found more Interface "
                                               "Association Descriptors "
                                               "than allocated for in "
                                               "configuration %d\n", cfgno);
                        } else {
-                               config->intf_assoc[iad_num] =
-                                       (struct usb_interface_assoc_descriptor
-                                       *)header;
+                               config->intf_assoc[iad_num] = d;
                                iad_num++;
                        }
 

diff --git a/include/uapi/linux/usb/ch9.h b/include/uapi/linux/usb/ch9.h
index a8acc24..5e64a86 100644 (file)
--- a/include/uapi/linux/usb/ch9.h
+++ b/include/uapi/linux/usb/ch9.h
@@ -759,6 +759,7 @@ struct usb_interface_assoc_descriptor {
        __u8  iFunction;
 } __attribute__ ((packed));
 
+#define USB_DT_INTERFACE_ASSOCIATION_SIZE      8
 
 /*-------------------------------------------------------------------------*/