tipc: check group dests after tipc_wait_for_cond()

Similar to commit 143ece65 ("tipc: check tsk->group in tipc_wait_for_cond()")
we have to reload grp->dests too after we re-take the sock lock.
This means we need to move the dsts check after tipc_wait_for_cond()
too.

Fixes: 75da2163 ("tipc: introduce communication groups")
Reported-and-tested-by: syzbot+99f20222fc5018d2b97a@syzkaller.appspotmail.com
Cc: Ying Xue <ying.xue@windriver.com>
Cc: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/socket.c

@@ -1009,7 +1009,7 @@ static int tipc_send_group_bcast(struct socket *sock, struct msghdr *m,
 	struct sock *sk = sock->sk;
 	struct net *net = sock_net(sk);
 	struct tipc_sock *tsk = tipc_sk(sk);
-	struct tipc_nlist *dsts = tipc_group_dests(tsk->group);
+	struct tipc_nlist *dsts;
 	struct tipc_mc_method *method = &tsk->mc_method;
 	bool ack = method->mandatory && method->rcast;
 	int blks = tsk_blocks(MCAST_H_SIZE + dlen);
@@ -1018,9 +1018,6 @@ static int tipc_send_group_bcast(struct socket *sock, struct msghdr *m,
 	struct sk_buff_head pkts;
 	int rc = -EHOSTUNREACH;
 
-	if (!dsts->local && !dsts->remote)
-		return -EHOSTUNREACH;
-
 	/* Block or return if any destination link or member is congested */
 	rc = tipc_wait_for_cond(sock, &timeout,
 				!tsk->cong_link_cnt && tsk->group &&
@@ -1028,6 +1025,10 @@ static int tipc_send_group_bcast(struct socket *sock, struct msghdr *m,
 	if (unlikely(rc))
 		return rc;
 
+	dsts = tipc_group_dests(tsk->group);
+	if (!dsts->local && !dsts->remote)
+		return -EHOSTUNREACH;
+
 	/* Complete message header */
 	if (dest) {
 		msg_set_type(hdr, TIPC_GRP_MCAST_MSG);