From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Horman Subject: Re: [net PATCH v3 3/3] net: netprio: fix cgrp create and write priomap race Date: Wed, 15 Aug 2012 06:56:18 -0400 Message-ID: <20120815105618.GC23811@hmsreliant.think-freely.org> References: <20120814223424.3551.21608.stgit@jf-dev1-dcblab> <20120814223435.3551.62387.stgit@jf-dev1-dcblab> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: viro@ZenIV.linux.org.uk, netdev@vger.kernel.org, davem@davemloft.net, linux-kernel@vger.kernel.org, joe@perches.com To: John Fastabend Return-path: Content-Disposition: inline In-Reply-To: <20120814223435.3551.62387.stgit@jf-dev1-dcblab> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, Aug 14, 2012 at 03:34:35PM -0700, John Fastabend wrote: > 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: > > Acked-by: Neil Horman