netdev - Re: [PATCH] vlan: fix potential race in vlan_cleanup_module vs vlan_ioctl

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Date:	Tue, 11 Dec 2007 11:38:38 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Pavel Emelyanov <xemul@...nvz.org>
CC:	David Miller <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>, devel@...nvz.org
Subject: Re: [PATCH] vlan: fix potential race in vlan_cleanup_module vs vlan_ioctl_handler

Pavel Emelyanov wrote:
> The vlan module cleanup function starts with
> 
> 	vlan_netlink_fini();
> 	vlan_ioctl_set(NULL);
> 
> The first call removes all the vlan devices and
> the second one closes the vlan ioctl.
> 
> AFAIS there's a tiny race window between these two
> calls - after rtnl unregistered all the vlans, but 
> the ioctl handler isn't set to NULL yet, user can 
> manage to call this ioctl and create one vlan device, 
> and that this function will later BUG_ON seeing 
> non-emply hashes.

Indeed, I can't see anything preventing this.

> I think, that we must first close the vlan ioctl
> and only after this remove all the vlans with the
> vlan_netlink_fini() call.

That looks correct, thanks Pavel. Dave, please apply.

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