[PATCH 4.19 105/113] tipc: fix hanging clients using poll with EPOLLOUT flag

[Greg Kroah-Hartman]

From: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@xxxxxxxxx>

[ Upstream commit ff946833b70e0c7f93de9a3f5b329b5ae2287b38 ]

commit 517d7c79bdb398 ("tipc: fix hanging poll() for stream sockets")
introduced a regression for clients using non-blocking sockets.
After the commit, we send EPOLLOUT event to the client even in
TIPC_CONNECTING state. This causes the subsequent send() to fail
with ENOTCONN, as the socket is still not in TIPC_ESTABLISHED state.

In this commit, we:
- improve the fix for hanging poll() by replacing sk_data_ready()
  with sk_state_change() to wake up all clients.
- revert the faulty updates introduced by commit 517d7c79bdb398
  ("tipc: fix hanging poll() for stream sockets").

Fixes: 517d7c79bdb398 ("tipc: fix hanging poll() for stream sockets")
Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@xxxxxxxxx>
Acked-by: Jon Maloy <jon.maloy@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/tipc/socket.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -726,11 +726,11 @@ static __poll_t tipc_poll(struct file *f
 
 	switch (sk->sk_state) {
 	case TIPC_ESTABLISHED:
-	case TIPC_CONNECTING:
 		if (!tsk->cong_link_cnt && !tsk_conn_cong(tsk))
 			revents |= EPOLLOUT;
 		/* fall thru' */
 	case TIPC_LISTEN:
+	case TIPC_CONNECTING:
 		if (!skb_queue_empty(&sk->sk_receive_queue))
 			revents |= EPOLLIN | EPOLLRDNORM;
 		break;
@@ -2039,7 +2039,7 @@ static bool tipc_sk_filter_connect(struc
 			return true;
 
 		/* If empty 'ACK-' message, wake up sleeping connect() */
-		sk->sk_data_ready(sk);
+		sk->sk_state_change(sk);
 
 		/* 'ACK-' message is neither accepted nor rejected: */
 		msg_set_dest_droppable(hdr, 1);