linux-kernel - [PATCH 4.4 44/54] rxrpc: Fix sendmsg() returning EPIPE due to recvmsg() returning ENODATA

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Date:   Thu, 30 Jul 2020 10:05:23 +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, David Howells <dhowells@...hat.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 44/54] rxrpc: Fix sendmsg() returning EPIPE due to recvmsg() returning ENODATA

From: David Howells <dhowells@...hat.com>

[ Upstream commit 639f181f0ee20d3249dbc55f740f0167267180f0 ]

rxrpc_sendmsg() returns EPIPE if there's an outstanding error, such as if
rxrpc_recvmsg() indicating ENODATA if there's nothing for it to read.

Change rxrpc_recvmsg() to return EAGAIN instead if there's nothing to read
as this particular error doesn't get stored in ->sk_err by the networking
core.

Also change rxrpc_sendmsg() so that it doesn't fail with delayed receive
errors (there's no way for it to report which call, if any, the error was
caused by).

Fixes: 17926a79320a ("[AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both")
Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/rxrpc/ar-output.c  |    2 +-
 net/rxrpc/ar-recvmsg.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/net/rxrpc/ar-output.c
+++ b/net/rxrpc/ar-output.c
@@ -533,7 +533,7 @@ static int rxrpc_send_data(struct rxrpc_
 	/* this should be in poll */
 	sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 
-	if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
+	if (sk->sk_shutdown & SEND_SHUTDOWN)
 		return -EPIPE;
 
 	more = msg->msg_flags & MSG_MORE;
--- a/net/rxrpc/ar-recvmsg.c
+++ b/net/rxrpc/ar-recvmsg.c
@@ -78,7 +78,7 @@ int rxrpc_recvmsg(struct socket *sock, s
 				release_sock(&rx->sk);
 				if (continue_call)
 					rxrpc_put_call(continue_call);
-				return -ENODATA;
+				return -EAGAIN;
 			}
 		}