USB: Fix slab-out-of-bounds write in usb_get_bos_descriptor

The syzkaller USB fuzzer found a slab-out-of-bounds write bug in the
USB core, caused by a failure to check the actual size of a BOS
descriptor.  This patch adds a check to make sure the descriptor is at
least as large as it is supposed to be, so that the code doesn't
inadvertently access memory beyond the end of the allocated region
when assigning to dev->bos->desc->bNumDeviceCaps later on.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-and-tested-by: syzbot+71f1e64501a309fcc012@syzkaller.appspotmail.com
CC: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index 20ff036b4c22d2812ff89732885d596e868f91e3..9d6cb709ca7bcf32eeb7e290ba5350da390d1ef5 100644 (file)
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -932,8 +932,8 @@ int usb_get_bos_descriptor(struct usb_device *dev)
 
        /* Get BOS descriptor */
        ret = usb_get_descriptor(dev, USB_DT_BOS, 0, bos, USB_DT_BOS_SIZE);
-       if (ret < USB_DT_BOS_SIZE) {
-               dev_err(ddev, "unable to get BOS descriptor\n");
+       if (ret < USB_DT_BOS_SIZE || bos->bLength < USB_DT_BOS_SIZE) {
+               dev_err(ddev, "unable to get BOS descriptor or descriptor too short\n");
                if (ret >= 0)
                        ret = -ENOMSG;
                kfree(bos);