From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Neil Brown , Trond Myklebust Subject: [PATCH 3.4 24/99] SUNRPC: Fix races in xs_nospace() Date: Fri, 7 Mar 2014 17:07:20 -0800 Message-Id: <20140308010612.392518072@linuxfoundation.org> In-Reply-To: <20140308010611.468206150@linuxfoundation.org> References: <20140308010611.468206150@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Trond Myklebust commit 06ea0bfe6e6043cb56a78935a19f6f8ebc636226 upstream. When a send failure occurs due to the socket being out of buffer space, we call xs_nospace() in order to have the RPC task wait until the socket has drained enough to make it worth while trying again. The current patch fixes a race in which the socket is drained before we get round to setting up the machinery in xs_nospace(), and which is reported to cause hangs. Link: http://lkml.kernel.org/r/20140210170315.33dfc621@notabene.brown Fixes: a9a6b52ee1ba (SUNRPC: Don't start the retransmission timer...) Reported-by: Neil Brown Signed-off-by: Trond Myklebust Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/xprtsock.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -501,6 +501,7 @@ static int xs_nospace(struct rpc_task *t struct rpc_rqst *req = task->tk_rqstp; struct rpc_xprt *xprt = req->rq_xprt; struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt); + struct sock *sk = transport->inet; int ret = -EAGAIN; dprintk("RPC: %5u xmit incomplete (%u left of %u)\n", @@ -518,7 +519,7 @@ static int xs_nospace(struct rpc_task *t * window size */ set_bit(SOCK_NOSPACE, &transport->sock->flags); - transport->inet->sk_write_pending++; + sk->sk_write_pending++; /* ...and wait for more buffer space */ xprt_wait_for_buffer_space(task, xs_nospace_callback); } @@ -528,6 +529,9 @@ static int xs_nospace(struct rpc_task *t } spin_unlock_bh(&xprt->transport_lock); + + /* Race breaker in case memory is freed before above code is called */ + sk->sk_write_space(sk); return ret; }