patch "USB: fix out-of-bounds in usb_set_configuration" added to usb-linus

This is a note to let you know that I've just added the patch titled

USB: fix out-of-bounds in usb_set_configuration

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From: Greg Kroah-Hartman <[email protected]>
Date: Tue, 19 Sep 2017 15:07:17 +0200
Subject: USB: fix out-of-bounds in usb_set_configuration

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...

---
 drivers/usb/core/config.c    | 14 +++++++++++---
 include/uapi/linux/usb/ch9.h |  1 +
 2 files changed, 12 insertions(+), 3 deletions(-)

index 854c8d66cfbe..68b54bd88d1e 100644
@@ -643,15 +643,23 @@ 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++;
 			}
 

index ce1169af39d7..2a5d63040a0b 100644
@@ -780,6 +780,7 @@ struct usb_interface_assoc_descriptor {
 	__u8  iFunction;
 } __attribute__ ((packed));
 
+#define USB_DT_INTERFACE_ASSOCIATION_SIZE	8
 
 /*-------------------------------------------------------------------------*/
 

2.14.1