commit c19483cc upstream.

Fortunately this is only exploitable on very unusual hardware.

[Reported a while ago but nothing happened so just fixing it]
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>