linux-kernel - [ 072/105] SUNRPC: Prevent races in xs_abort

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Message-Id: <20121028231559.221965031@decadent.org.uk>
Date:	Sun, 28 Oct 2012 23:16:48 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	Chris Perl <chris.perl@...il.com>
Subject: [ 072/105] SUNRPC: Prevent races in xs_abort_connection()

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

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

From: Trond Myklebust <Trond.Myklebust@...app.com>

commit 4bc1e68ed6a8b59be8a79eb719be515a55c7bc68 upstream.

The call to xprt_disconnect_done() that is triggered by a successful
connection reset will trigger another automatic wakeup of all tasks
on the xprt->pending rpc_wait_queue. In particular it will cause an
early wake up of the task that called xprt_connect().

All we really want to do here is clear all the socket-specific state
flags, so we split that functionality out of xs_sock_mark_closed()
into a helper that can be called by xs_abort_connection()

Reported-by: Chris Perl <chris.perl@...il.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
Tested-by: Chris Perl <chris.perl@...il.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/sunrpc/xprtsock.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 7e2dd0d..1f105c2 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1453,7 +1453,7 @@ static void xs_tcp_cancel_linger_timeout(struct rpc_xprt *xprt)
 	xprt_clear_connecting(xprt);
 }
 
-static void xs_sock_mark_closed(struct rpc_xprt *xprt)
+static void xs_sock_reset_connection_flags(struct rpc_xprt *xprt)
 {
 	smp_mb__before_clear_bit();
 	clear_bit(XPRT_CONNECTION_ABORT, &xprt->state);
@@ -1461,6 +1461,11 @@ static void xs_sock_mark_closed(struct rpc_xprt *xprt)
 	clear_bit(XPRT_CLOSE_WAIT, &xprt->state);
 	clear_bit(XPRT_CLOSING, &xprt->state);
 	smp_mb__after_clear_bit();
+}
+
+static void xs_sock_mark_closed(struct rpc_xprt *xprt)
+{
+	xs_sock_reset_connection_flags(xprt);
 	/* Mark transport as closed and wake up all pending tasks */
 	xprt_disconnect_done(xprt);
 }
@@ -2051,10 +2056,8 @@ static void xs_abort_connection(struct sock_xprt *transport)
 	any.sa_family = AF_UNSPEC;
 	result = kernel_connect(transport->sock, &any, sizeof(any), 0);
 	if (!result)
-		xs_sock_mark_closed(&transport->xprt);
-	else
-		dprintk("RPC:       AF_UNSPEC connect return code %d\n",
-				result);
+		xs_sock_reset_connection_flags(&transport->xprt);
+	dprintk("RPC:       AF_UNSPEC connect return code %d\n", result);
 }
 
 static void xs_tcp_reuse_connection(struct sock_xprt *transport)


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