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
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 5e6136d2ed71dbb39563f05f361e5e21d3c9ac7c..eb12eea1377071aa7327c6e12812d392171b3055 100644 (file)
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -931,8 +931,8 @@ 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);