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USB: core: fix out-of-bounds access bug in usb_get_bos_descriptor() 

Andrey used the syzkaller fuzzer to find an out-of-bounds memory
access in usb_get_bos_descriptor().  The code wasn't checking that the
next usb_dev_cap_header structure could fit into the remaining buffer
space.

This patch fixes the error and also reduces the bNumDeviceCaps field
in the header to match the actual number of capabilities found, in
cases where there are fewer than expected.

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
CC: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alan Stern 2017-10-18 12:49:38 -04:00 committed by Greg Kroah-Hartman
parent 671632a019
commit 1c0edc3633
1 changed files with 4 additions and 2 deletions
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6
drivers/usb/core/config.c
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@ -960,10 +960,12 @@ int usb_get_bos_descriptor(struct usb_device *dev)
for (i = 0; i < num; i++) {
buffer += length;
cap = (struct usb_dev_cap_header *)buffer;
length = cap->bLength;
if (total_len < length)
if (total_len < sizeof(*cap) || total_len < cap->bLength) {
dev->bos->desc->bNumDeviceCaps = i;
break;
}
length = cap->bLength;
total_len -= length;
if (cap->bDescriptorType != USB_DT_DEVICE_CAPABILITY) {