AFS: Potential null dereference

It seems clear from the surrounding code that xpermits is allowed to be
NULL here.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/afs/security.c

@@ -189,8 +189,9 @@ void afs_cache_permit(struct afs_vnode *vnode, struct key *key, long acl_order)
 	if (!permits)
 		goto out_unlock;
 
-	memcpy(permits->permits, xpermits->permits,
-	       count * sizeof(struct afs_permit));
+	if (xpermits)
+		memcpy(permits->permits, xpermits->permits,
+			count * sizeof(struct afs_permit));
 
 	_debug("key %x access %x",
 	       key_serial(key), vnode->status.caller_access);