netdev - Re: [PATCH 1/1] packet: race condition in packet

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Date:	Thu, 05 Nov 2015 14:51:08 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	fruggeri@...stanetworks.com
Cc:	edumazet@...gle.com, netdev@...r.kernel.org, noureddine@...sta.com,
	fruggeri@...sta.com
Subject: Re: [PATCH 1/1] packet: race condition in packet_bind

From: fruggeri@...stanetworks.com (Francesco Ruggeri)
Date: Thu, 05 Nov 2015 08:16:14 -0800

> There is a race conditions between packet_notifier and packet_bind{_spkt}.
> 
> It happens if packet_notifier(NETDEV_UNREGISTER) executes between the
> time packet_bind{_spkt} takes a reference on the new netdevice and the
> time packet_do_bind sets po->ifindex.
> In this case the notification can be missed.
> If this happens during a dev_change_net_namespace this can result in the
> netdevice to be moved to the new namespace while the packet_sock in the
> old namespace still holds a reference on it. When the netdevice is later
> deleted in the new namespace the deletion hangs since the packet_sock
> is not found in the new namespace' &net->packet.sklist.
> It can be reproduced with the script below.
> 
> This patch makes packet_do_bind check again for the presence of the
> netdevice in the packet_sock's namespace after the synchronize_net
> in unregister_prot_hook.
> More in general it also uses the rcu lock for the duration of the bind
> to stop dev_change_net_namespace/rollback_registered_many from
> going past the synchronize_net following unlist_netdevice, so that
> no NETDEV_UNREGISTER notifications can happen on the new netdevice
> while the bind is executing. In order to do this some code from
> packet_bind{_spkt} is consolidated into packet_do_dev.
 ...
> Signed-off-by: Francesco Ruggeri <fruggeri@...sta.com>

Looks good, applied and queued up for -stable, thanks.
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