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net: netprio: fix cgrp create and write priomap race

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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>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
John Fastabend 2012-08-14 12:34:35 +00:00 committed by David S. Miller
parent 48a87cc26c
commit 476ad154f3
1 changed files with 3 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
net/core/netprio_cgroup.c
View file

@ -101,12 +101,10 @@ static int write_update_netdev_table(struct net_device *dev)
u32 max_len; u32 max_len;
struct netprio_map *map; struct netprio_map *map;
rtnl_lock();
max_len = atomic_read(&max_prioidx) + 1; max_len = atomic_read(&max_prioidx) + 1;
map = rtnl_dereference(dev->priomap); map = rtnl_dereference(dev->priomap);
if (!map || map->priomap_len < max_len) if (!map || map->priomap_len < max_len)
ret = extend_netdev_table(dev, max_len); ret = extend_netdev_table(dev, max_len);
rtnl_unlock();
return ret; return ret;
} }
@ -256,17 +254,17 @@ static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
if (!dev) if (!dev)
goto out_free_devname; goto out_free_devname;
rtnl_lock();
ret = write_update_netdev_table(dev); ret = write_update_netdev_table(dev);
if (ret < 0) if (ret < 0)
goto out_put_dev; goto out_put_dev;
rcu_read_lock(); map = rtnl_dereference(dev->priomap);
map = rcu_dereference(dev->priomap);
if (map) if (map)
map->priomap[prioidx] = priority; map->priomap[prioidx] = priority;
rcu_read_unlock();
out_put_dev: out_put_dev:
rtnl_unlock();
dev_put(dev); dev_put(dev);
out_free_devname: out_free_devname: