netdev - Re: [PATCH net] net: ipmr, ip6mr: fix vif/tunnel failure race condition

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Date:	Tue, 24 Nov 2015 10:56:46 -0800
From:	Cong Wang <cwang@...pensource.com>
To:	Nikolay Aleksandrov <razor@...ckwall.org>
Cc:	netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Subject: Re: [PATCH net] net: ipmr, ip6mr: fix vif/tunnel failure race condition

On Tue, Nov 24, 2015 at 8:09 AM, Nikolay Aleksandrov
<razor@...ckwall.org> wrote:
> From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
>
> Since (at least) commit b17a7c179dd3 ("[NET]: Do sysfs registration as
> part of register_netdevice."), netdev_run_todo() deals only with
> unregistration, so we don't need to do the rtnl_unlock/lock cycle to
> finish registration when failing pimreg or dvmrp device creation. In
> fact that opens a race condition where someone can delete the device
> while rtnl is unlocked because it's fully registered. The problem gets
> worse when netlink support is introduced as there are more points of entry
> that can cause it and it also makes reusing that code correctly impossible.
>
> Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>

Makes sense for me, we do have some other cases (e.g. macvlan) where
we call unregister_netdevice() in error path without re-taking RTNL lock.

So,

Reviewed-by: Cong Wang <cwang@...pensource.com>

Thanks.
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