cgroup: fix panic in netprio_cgroup

we set max_prioidx to the first zero bit index of prioidx_map in
function get_prioidx.

So when we delete the low index netprio cgroup and adding a new
netprio cgroup again,the max_prioidx will be set to the low index.

when we set the high index cgroup's net_prio.ifpriomap,the function
write_priomap will call update_netdev_tables to alloc memory which
size is sizeof(struct netprio_map) + sizeof(u32) * (max_prioidx + 1),
so the size of array that map->priomap point to is max_prioidx +1,
which is low than what we actually need.

fix this by adding check in get_prioidx,only set max_prioidx when
max_prioidx low than the new prioidx.

Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 5b8aa2fae48b84e3255ecdfe83535457bd170901..aa907ed466ead3ef5b0b585843783af9e384dedf 100644 (file)
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -49,8 +49,9 @@ static int get_prioidx(u32 *prio)
                return -ENOSPC;
        }
        set_bit(prioidx, prioidx_map);
+       if (atomic_read(&max_prioidx) < prioidx)
+               atomic_set(&max_prioidx, prioidx);
        spin_unlock_irqrestore(&prioidx_map_lock, flags);
-       atomic_set(&max_prioidx, prioidx);
        *prio = prioidx;
        return 0;
 }