From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754032Ab3BCOzn (ORCPT ); Sun, 3 Feb 2013 09:55:43 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:34217 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753462Ab3BCOzj (ORCPT ); Sun, 3 Feb 2013 09:55:39 -0500 Message-Id: <20130203144646.508344097@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Sun, 03 Feb 2013 15:47:12 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, Trond Myklebust , Chris Perl Subject: [ 028/128] SUNRPC: Ensure we release the socket write lock if the rpc_task exits early In-Reply-To: <20130203144644.035172954@decadent.org.uk> X-SA-Exim-Connect-IP: 151.216.67.5 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Trond Myklebust commit 87ed50036b866db2ec2ba16b2a7aec4a2b0b7c39 upstream. If the rpc_task exits while holding the socket write lock before it has allocated an rpc slot, then the usual mechanism for releasing the write lock in xprt_release() is defeated. The problem occurs if the call to xprt_lock_write() initially fails, so that the rpc_task is put on the xprt->sending wait queue. If the task exits after being assigned the lock by __xprt_lock_write_func, but before it has retried the call to xprt_lock_and_alloc_slot(), then it calls xprt_release() while holding the write lock, but will immediately exit due to the test for task->tk_rqstp != NULL. Reported-by: Chris Perl Signed-off-by: Trond Myklebust Signed-off-by: Ben Hutchings --- net/sunrpc/sched.c | 3 +-- net/sunrpc/xprt.c | 12 ++++++++++-- 2 files changed, 11 insertions(+), 4 deletions(-) --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -918,8 +918,7 @@ static void rpc_async_release(struct wor static void rpc_release_resources_task(struct rpc_task *task) { - if (task->tk_rqstp) - xprt_release(task); + xprt_release(task); if (task->tk_msg.rpc_cred) { put_rpccred(task->tk_msg.rpc_cred); task->tk_msg.rpc_cred = NULL; --- a/net/sunrpc/xprt.c +++ b/net/sunrpc/xprt.c @@ -1132,10 +1132,18 @@ static void xprt_request_init(struct rpc void xprt_release(struct rpc_task *task) { struct rpc_xprt *xprt; - struct rpc_rqst *req; + struct rpc_rqst *req = task->tk_rqstp; - if (!(req = task->tk_rqstp)) + if (req == NULL) { + if (task->tk_client) { + rcu_read_lock(); + xprt = rcu_dereference(task->tk_client->cl_xprt); + if (xprt->snd_task == task) + xprt_release_write(xprt, task); + rcu_read_unlock(); + } return; + } xprt = req->rq_xprt; rpc_count_iostats(task);