xenbus_xs.c: fix a use-after-free

This patch fixes an obvious use-after-free spotted by the Coverity checker.
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Acked-by: NJeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/xen/xenbus/xenbus_xs.c

@@ -782,8 +782,8 @@ static int process_msg(void)
 		msg->u.watch.vec = split(body, msg->hdr.len,
 					 &msg->u.watch.vec_size);
 		if (IS_ERR(msg->u.watch.vec)) {
-			kfree(msg);
 			err = PTR_ERR(msg->u.watch.vec);
+			kfree(msg);
 			goto out;
 		}