drm/xe: Fix access_ok check in user_fence_create

Check size of the data not size of the pointer.

Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Fixes: ddeb798 ("drm/xe: Validate user fence during creation")
Cc: Matthew Auld <[email protected]>
Cc: Matthew Brost <[email protected]>
Reviewed-by: Matthew Auld <[email protected]>
Reviewed-by: Tejas Upadhyay <[email protected]>
Reviewed-by: Apoorva Singh <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Nirmoy Das <[email protected]>
(cherry picked from commit e102b5e)
Signed-off-by: Rodrigo Vivi <[email protected]>

Author: nirmoy

drivers/gpu/drm/xe/xe_sync.c

@@ -55,7 +55,7 @@ static struct xe_user_fence *user_fence_create(struct xe_device *xe, u64 addr,
 	struct xe_user_fence *ufence;
 	u64 __user *ptr = u64_to_user_ptr(addr);
 
-	if (!access_ok(ptr, sizeof(ptr)))
+	if (!access_ok(ptr, sizeof(*ptr)))
 		return ERR_PTR(-EFAULT);
 
 	ufence = kmalloc(sizeof(*ufence), GFP_KERNEL);