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SubjectRe: [net PATCH v3 3/3] net: netprio: fix cgrp create and write priomap race
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 <nhorman@tuxdriver.com>
> Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
> Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
> ---
>
> 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 <nhorman@tuxdriver.com>



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