netdev - Re: [PATCH net] net: avoid potential UAF in default

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Message-ID: <CANn89i+hjGLeGd-wFi+CS=HkrvcHtTso74qJVFLk44cVqid92g@mail.gmail.com>
Date: Wed, 4 Dec 2024 12:46:11 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Vladimir Oltean <vladimir.oltean@....com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	syzbot+1939f24bdb783e9e43d9@...kaller.appspotmail.com
Subject: Re: [PATCH net] net: avoid potential UAF in default_operstate()

On Wed, Dec 4, 2024 at 12:41 PM Vladimir Oltean <vladimir.oltean@....com> wrote:
>
> I meant: linkwatch runs periodically, via linkwatch_event(). Isn't there
> a chance that linkwatch_event() can run once, immediately after
> __rtnl_unlock() in netdev_run_todo(), while the netdev is in the
> NETREG_UNREGISTERING state? Won't that create problems for __dev_get_by_index()
> too? I guess it depends on when the netns is torn down, which I couldn't find.

I think lweventlist_lock and dev->link_watch_list are supposed to
synchronize things.

linkwatch_sync_dev() only calls linkwatch_do_dev() if the device was
atomically unlinked from lweventlist