tipc: fix cancellation of topology subscriptions

[ Upstream commit 33872d79f5d1cbedaaab79669cc38f16097a9450 ]

When cancelling a subscription, we have to clear the cancel bit in the
request before iterating over any established subscriptions with memcmp.
Otherwise no subscription will ever be found, and it will not be
possible to explicitly unsubscribe individual subscriptions.

Fixes: 8985ecc7c1e0 ("tipc: simplify endianness handling in topology subscriber")
Signed-off-by: Erik Hugne <erik.hugne@gmail.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/tipc/topsrv.c

@@ -371,6 +371,7 @@ static int tipc_conn_rcv_sub(struct tipc_topsrv *srv,
 	struct tipc_subscription *sub;
 
 	if (tipc_sub_read(s, filter) & TIPC_SUB_CANCEL) {
+		s->filter &= __constant_ntohl(~TIPC_SUB_CANCEL);
 		tipc_conn_delete_sub(con, s);
 		return 0;
 	}