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

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Date:	Tue, 24 Nov 2015 17:16:27 -0500 (EST)
From:	David Miller <davem@...hat.com>
To:	razor@...ckwall.org
Cc:	netdev@...r.kernel.org, yoshfuji@...ux-ipv6.org,
	nikolay@...ulusnetworks.com
Subject: Re: [PATCH net] net: ipmr, ip6mr: fix vif/tunnel failure race
 condition

From: Nikolay Aleksandrov <razor@...ckwall.org>
Date: Tue, 24 Nov 2015 17:09:30 +0100

> 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>
> ---
> I was able to crash the kernel by artificially triggering this race just to
> confim it. I know it's very unlikely to hit the race in the real world, but
> the biggest advantage of the change is that the code can be re-used later
> when adding netlink support.

Applied, thank you.
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