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

commit a03ff54460817c76105f81f3aa8ef655759ccc9a upstream.

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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index cee00dc829b6d69a6b2d584c91940afecc87a67f..52dfe4936a0f3fc857343d9ba5980542c4e346e3 100644 (file)
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -897,8 +897,8 @@ 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);