linux-kernel - [PATCH 4.12 150/196] net/sunrpc/xprt_sock: fix regression in connection error reporting.

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Message-Id: <20170725192053.372367390@linuxfoundation.org>
Date:   Tue, 25 Jul 2017 12:22:29 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, NeilBrown <neilb@...e.com>,
        Anna Schumaker <Anna.Schumaker@...app.com>
Subject: [PATCH 4.12 150/196] net/sunrpc/xprt_sock: fix regression in connection error reporting.

4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: NeilBrown <neilb@...e.com>

commit 3ffbc1d65583394be12801655781dd2b079ce169 upstream.

Commit 3d4762639dd3 ("tcp: remove poll() flakes when receiving
RST") in v4.12 changed the order in which ->sk_state_change()
and ->sk_error_report() are called when a socket is shut
down - sk_state_change() is now called first.

This causes xs_tcp_state_change() -> xs_sock_mark_closed() ->
xprt_disconnect_done() to wake all pending tasked with -EAGAIN.
When the ->sk_error_report() callback arrives, it is too late to
pass the error on, and it is lost.

As easy way to demonstrate the problem caused is to try to start
rpc.nfsd while rcpbind isn't running.
nfsd will attempt a tcp connection to rpcbind.  A ECONNREFUSED
error is returned, but sunrpc code loses the error and keeps
retrying.  If it saw the ECONNREFUSED, it would abort.

To fix this, handle the sk->sk_err in the TCP_CLOSE branch of
xs_tcp_state_change().

Fixes: 3d4762639dd3 ("tcp: remove poll() flakes when receiving RST")
Signed-off-by: NeilBrown <neilb@...e.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/sunrpc/xprtsock.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1624,6 +1624,8 @@ static void xs_tcp_state_change(struct s
 		if (test_and_clear_bit(XPRT_SOCK_CONNECTING,
 					&transport->sock_state))
 			xprt_clear_connecting(xprt);
+		if (sk->sk_err)
+			xprt_wake_pending_tasks(xprt, -sk->sk_err);
 		xs_sock_mark_closed(xprt);
 	}
  out: