From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Fastabend Subject: [net PATCH v3 3/3] net: netprio: fix cgrp create and write priomap race Date: Tue, 14 Aug 2012 15:34:35 -0700 Message-ID: <20120814223435.3551.62387.stgit@jf-dev1-dcblab> References: <20120814223424.3551.21608.stgit@jf-dev1-dcblab> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, davem@davemloft.net, linux-kernel@vger.kernel.org, joe@perches.com To: viro@ZenIV.linux.org.uk, nhorman@tuxdriver.com Return-path: In-Reply-To: <20120814223424.3551.21608.stgit@jf-dev1-dcblab> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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 --- net/core/netprio_cgroup.c | 8 +++----- 1 files changed, 3 insertions(+), 5 deletions(-) diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c index f65dba3..c75e3f9 100644 --- a/net/core/netprio_cgroup.c +++ b/net/core/netprio_cgroup.c @@ -101,12 +101,10 @@ 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; } @@ -256,17 +254,17 @@ 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: