From: Tuong Lien <tuong.t.lien@dektech.com.au>
Date: Mon, 4 May 2020 11:15:54 +0700
Subject: tipc: fix partial topology connection closure
Git-commit: 980d69276f3048af43a045be2925dacfb898a7be
Patch-mainline: 5.7-rc5
References: networking-stable-20_05_12

When an application connects to the TIPC topology server and subscribes
to some services, a new connection is created along with some objects -
'tipc_subscription' to store related data correspondingly...
However, there is one omission in the connection handling that when the
connection or application is orderly shutdown (e.g. via SIGQUIT, etc.),
the connection is not closed in kernel, the 'tipc_subscription' objects
are not freed too.
This results in:
- The maximum number of subscriptions (65535) will be reached soon, new
subscriptions will be rejected;
- TIPC module cannot be removed (unless the objects  are somehow forced
to release first);

The commit fixes the issue by closing the connection if the 'recvmsg()'
returns '0' i.e. when the peer is shutdown gracefully. It also includes
the other unexpected cases.

Acked-by: Jon Maloy <jmaloy@redhat.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Tuong Lien <tuong.t.lien@dektech.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 net/tipc/topsrv.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/tipc/topsrv.c
+++ b/net/tipc/topsrv.c
@@ -401,10 +401,11 @@ static int tipc_conn_rcv_from_sock(struc
 		read_lock_bh(&sk->sk_callback_lock);
 		ret = tipc_conn_rcv_sub(srv, con, &s);
 		read_unlock_bh(&sk->sk_callback_lock);
+		if (!ret)
+			return 0;
 	}
-	if (ret < 0)
-		tipc_conn_close(con);
 
+	tipc_conn_close(con);
 	return ret;
 }