From: <wyb@xxxxxxxxxxxxx>
Date: Wed, 16 Jan 2008 18:04:53 +0800
> 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:
netdev@xxxxxxxxxxxxxxx (CC:'d) is the proper place to report
things like this.
'linux-net' is only for general user questions about the networking,
not for bug reports, patch postings, or developer discussion. The
'netdev' list is for that.
Thank you.
>
> 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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