netdev - Re: [patch net] net: fix ifindex collision during namespace removal

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Message-Id: <20190729.110807.1476818178420042682.davem@davemloft.net>
Date:   Mon, 29 Jul 2019 11:08:07 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     jiri@...nulli.us
Cc:     netdev@...r.kernel.org, xemul@...tuozzo.com, edumazet@...gle.com,
        pabeni@...hat.com, idosch@...lanox.com, petrm@...lanox.com,
        sd@...asysnail.net, f.fainelli@...il.com,
        stephen@...workplumber.org, mlxsw@...lanox.com, jiri@...lanox.com
Subject: Re: [patch net] net: fix ifindex collision during namespace removal

From: Jiri Pirko <jiri@...nulli.us>
Date: Sun, 28 Jul 2019 14:56:36 +0200

> From: Jiri Pirko <jiri@...lanox.com>
> 
> Commit aca51397d014 ("netns: Fix arbitrary net_device-s corruptions
> on net_ns stop.") introduced a possibility to hit a BUG in case device
> is returning back to init_net and two following conditions are met:
> 1) dev->ifindex value is used in a name of another "dev%d"
>    device in init_net.
> 2) dev->name is used by another device in init_net.
> 
> Under real life circumstances this is hard to get. Therefore this has
> been present happily for over 10 years. To reproduce:
 ...
> Fix this by checking if a device with the same name exists in init_net
> and fallback to original code - dev%d to allocate name - in case it does.
> 
> This was found using syzkaller.
> 
> Fixes: aca51397d014 ("netns: Fix arbitrary net_device-s corruptions on net_ns stop.")
> Signed-off-by: Jiri Pirko <jiri@...lanox.com>

Very interesting :)

Applied and queued up for -stable, thanks.