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Subject[PATCH 4.4 29/47] USB: fix out-of-bounds in usb_set_configuration
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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>

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

--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -609,15 +609,23 @@ static int usb_parse_configuration(struc

} 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++;
}

--- a/include/uapi/linux/usb/ch9.h
+++ b/include/uapi/linux/usb/ch9.h
@@ -717,6 +717,7 @@ struct usb_interface_assoc_descriptor {
__u8 iFunction;
} __attribute__ ((packed));

+#define USB_DT_INTERFACE_ASSOCIATION_SIZE 8

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


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