drm/xe/ufence: Prefetch ufence addr to catch bogus address

[ Upstream commit 9c1813b3 ]

access_ok() only checks for addr overflow so also try to read the addr
to catch invalid addr sent from userspace.

Link: drm/xe/kernel#1630


Cc: Francois Dugast <francois.dugast@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241016082304.66009-2-nirmoy.das@intel.com


Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
(cherry picked from commit 9408c450)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>