netdev - Re: memory leakage in bridge(kernel-2.6.23.14)

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Date:	Wed, 16 Jan 2008 04:31:06 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	wyb@...sec.com.cn
Cc:	linux-net@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: memory leakage in bridge(kernel-2.6.23.14)

From: <wyb@...sec.com.cn>
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@...r.kernel.org (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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