SUNRPC: Prevent races in xs_abort_connection()

commit 4bc1e68e 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@gmail.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Tested-by: Chris Perl <chris.perl@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

net/sunrpc/xprtsock.c

@@ -1465,7 +1465,7 @@ 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);
@@ -1473,6 +1473,11 @@ 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);
 }
@@ -2028,10 +2033,8 @@ 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)