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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...

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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gregkh committed Sep 19, 2017
1 parent bcd6a7a commit bd7a3fe770ebd8391d1c7d072ff88e9e76d063eb
Showing with 12 additions and 3 deletions.
  1. +11 −3 drivers/usb/core/config.c
  2. +1 −0 include/uapi/linux/usb/ch9.h
@@ -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++;
}

@@ -780,6 +780,7 @@ struct usb_interface_assoc_descriptor {
__u8 iFunction;
} __attribute__ ((packed));

#define USB_DT_INTERFACE_ASSOCIATION_SIZE 8

/*-------------------------------------------------------------------------*/

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