usb: core: fix slab-out-of-bounds Read in read_descriptors

commit a18cd6c9b6bc73dc17e8b7e9bd07decaa8833c97 upstream.

The USB device descriptor may get changed between two consecutive
enumerations on the same device for some reason, such as DFU or
malicius device.
In that case, we may access the changing descriptor if we don't take
the device lock here.

The issue is reported:
https://syzkaller.appspot.com/bug?id=901a0d9e6519ef8dc7acab25344bd287dd3c7be9



Cc: stable <stable@vger.kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Reported-by:  <syzbot+256e56ddde8b8957eabd@syzkaller.appspotmail.com>
Fixes: 217a9081 ("USB: add all configs to the "descriptors" attribute")
Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com>
Link: https://lore.kernel.org/r/1599201467-11000-1-git-send-email-prime.zeng@hisilicon.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>