netdev - Re: [PATCH v4 net 3/3] dev: Use rtnl_net_dev_lock() in unregister

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Message-ID: <CANn89iKAKfW36RdwAvvSogLPL52bnLhrV-PKz_u7oJ8GrL4-sQ@mail.gmail.com>
Date: Wed, 12 Feb 2025 14:55:33 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v4 net 3/3] dev: Use rtnl_net_dev_lock() in unregister_netdev().

On Wed, Feb 12, 2025 at 7:43 AM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
>
> The following sequence is basically illegal when dev was fetched
> without lookup because dev_net(dev) might be different after holding
> rtnl_net_lock():
>
>   net = dev_net(dev);
>   rtnl_net_lock(net);
>
> Let's use rtnl_net_dev_lock() in unregister_netdev().
>
> Note that there is no real bug in unregister_netdev() for now
> because RTNL protects the scope even if dev_net(dev) is changed
> before/after RTNL.
>
> Fixes: 00fb9823939e ("dev: Hold per-netns RTNL in (un)?register_netdev().")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>

Reviewed-by: Eric Dumazet <edumazet@...gle.com>