AFS: Fix cache manager service handlers

Fix the cache manager RPC service handlers.  The afs_send_empty_reply() and
afs_send_simple_reply() functions:

 (a) Kill the call and free up the buffers associated with it if they fail.

 (b) Return with call intact if it they succeed.

However, none of the callers actually check the result or clean up if
successful - and may use the now non-existent data if it fails.

This was detected by Dan Carpenter using a static checker:

	The patch 08e0e7c82e: "[AF_RXRPC]: Make the in-kernel AFS
	filesystem use AF_RXRPC." from Apr 26, 2007, leads to the following
	static checker warning:
	"fs/afs/cmservice.c:155 SRXAFSCB_CallBack()
		 warn: 'call' was already freed."

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/cmservice.c

@@ -130,6 +130,15 @@ static void afs_cm_destructor(struct afs_call *call)
 {
 	_enter("");
 
+	/* Break the callbacks here so that we do it after the final ACK is
+	 * received.  The step number here must match the final number in
+	 * afs_deliver_cb_callback().
+	 */
+	if (call->unmarshall == 6) {
+		ASSERT(call->server && call->count && call->request);
+		afs_break_callbacks(call->server, call->count, call->request);
+	}
+
 	afs_put_server(call->server);
 	call->server = NULL;
 	kfree(call->buffer);
@@ -272,6 +281,16 @@ static int afs_deliver_cb_callback(struct afs_call *call, struct sk_buff *skb,
 		_debug("trailer");
 		if (skb->len != 0)
 			return -EBADMSG;
+
+		/* Record that the message was unmarshalled successfully so
+		 * that the call destructor can know do the callback breaking
+		 * work, even if the final ACK isn't received.
+		 *
+		 * If the step number changes, then afs_cm_destructor() must be
+		 * updated also.
+		 */
+		call->unmarshall++;
+	case 6:
 		break;
 	}