From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: [PATCH 3.4.y 3/3] net: netprio: fix cgrp create and write priomap race Date: Sat, 26 Jan 2013 12:42:22 +0800 Message-ID: <51035EAE.5090004@huawei.com> References: <51035E4F.6030508@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit Cc: , Gao feng , John Fastabend , Neil Horman To: David Miller Return-path: Received: from szxga02-in.huawei.com ([119.145.14.65]:38987 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750907Ab3AZEmd (ORCPT ); Fri, 25 Jan 2013 23:42:33 -0500 In-Reply-To: <51035E4F.6030508@huawei.com> Sender: netdev-owner@vger.kernel.org List-ID: From: John Fastabend commit 476ad154f3b41dd7d9a08a2f641e28388abc2fd1 upstream. A race exists where creating cgroups and also updating the priomap may result in losing a priomap update. This is because priomap writers are not protected by rtnl_lock. Move priority writer into rtnl_lock()/rtnl_unlock(). CC: Neil Horman Reported-by: Al Viro Signed-off-by: John Fastabend Acked-by: Neil Horman Signed-off-by: David S. Miller Signed-off-by: Li Zefan --- net/core/netprio_cgroup.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c index dca347e..eb07ea9 100644 --- a/net/core/netprio_cgroup.c +++ b/net/core/netprio_cgroup.c @@ -112,12 +112,10 @@ static int write_update_netdev_table(struct net_device *dev) u32 max_len; struct netprio_map *map; - rtnl_lock(); max_len = atomic_read(&max_prioidx) + 1; map = rtnl_dereference(dev->priomap); if (!map || map->priomap_len < max_len) ret = extend_netdev_table(dev, max_len); - rtnl_unlock(); return ret; } @@ -267,17 +265,17 @@ static int write_priomap(struct cgroup *cgrp, struct cftype *cft, if (!dev) goto out_free_devname; + rtnl_lock(); ret = write_update_netdev_table(dev); if (ret < 0) goto out_put_dev; - rcu_read_lock(); - map = rcu_dereference(dev->priomap); + map = rtnl_dereference(dev->priomap); if (map) map->priomap[prioidx] = priority; - rcu_read_unlock(); out_put_dev: + rtnl_unlock(); dev_put(dev); out_free_devname: -- 1.8.0.2