In SMP, if a bridge fdb is being created when another CPU at the same time
delete the bridge, this newly created fdb may incur a leakage:
CPU0:
static void del_nbp(struct net_bridge_port *p)
{
/*
* CPU1 enter br_fdb_update(), bridge port is still valid.
*/
......
spin_lock_bh(&br->lock);
br_stp_disable_port(p);
spin_unlock_bh(&br->lock);
br_ifinfo_notify(RTM_DELLINK, p);
br_fdb_delete_by_port(br, p, 1);
/*
* CPU1 call fdb_create() for the being deleted bridge,
* a fdb would be add to bridge's fdb hash table, and will never
* be freed. because when deleting a bridge, linux flush fdb for
each
* bridge port, but this newly created fdb belong to no bridge port
*/
......
}
To fix this, fdb_create() should be changed to:
{
struct net_bridge_fdb_entry *fdb;
/*
* if the bridge port is deleted, then return.
*/
if (!(source->state == BR_STATE_LEARNING ||
source->state == BR_STATE_FORWARDING))
return;
fdb = kmem_cache_alloc(br_fdb_cache, GFP_ATOMIC);
if (fdb) {
memcpy(fdb->addr.addr, addr, ETH_ALEN);
atomic_set(&fdb->use_count, 1);
hlist_add_head_rcu(&fdb->hlist, head);
fdb->dst = source;
fdb->is_local = is_local;
fdb->is_static = is_local;
fdb->ageing_timer = jiffies;
}
return fdb;
}
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