linux-kernel - [PATCH 5.1 26/46] tipc: fix hanging clients using poll with EPOLLOUT flag

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Message-Id: <20190515090625.299804305@linuxfoundation.org>
Date:   Wed, 15 May 2019 12:56:50 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@...il.com>,
        Jon Maloy <jon.maloy@...csson.se>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 5.1 26/46] tipc: fix hanging clients using poll with EPOLLOUT flag

From: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@...il.com>

[ 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@...il.com>
Acked-by: Jon Maloy <jon.maloy@...csson.se>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/tipc/socket.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -734,11 +734,11 @@ 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 through */
 	case TIPC_LISTEN:
+	case TIPC_CONNECTING:
 		if (!skb_queue_empty(&sk->sk_receive_queue))
 			revents |= EPOLLIN | EPOLLRDNORM;
 		break;
@@ -2041,7 +2041,7 @@ static bool tipc_sk_filter_connect(struc
 			if (msg_data_sz(hdr))
 				return true;
 			/* Empty ACK-, - wake up sleeping connect() and drop */
-			sk->sk_data_ready(sk);
+			sk->sk_state_change(sk);
 			msg_set_dest_droppable(hdr, 1);
 			return false;
 		}