netdev - Re: [PATCH net] net: read dev->needs_free_netdev before potentially freeing dev

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Message-ID: <CAHmME9q_5Vv8La7RR2XU48LFafEsGa1VWC1tZ+SWjcww_uyJZw@mail.gmail.com>
Date:   Mon, 24 Aug 2020 22:35:24 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Netdev <netdev@...r.kernel.org>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH net] net: read dev->needs_free_netdev before potentially
 freeing dev

On Mon, Aug 24, 2020 at 10:07 PM Jason A. Donenfeld <Jason@...c4.com> wrote:
> I believe that the bug Dan reported would easily be fixed as well by
> just setting dev->needs_free_netdev=true and removing the call to
> free_netdev(dev) in wg_destruct, in wireguard. If you think that this is
> the more proper fix -- and that the problem actually isn't this flow in
> dev.c and any code that might hit this UaF is wrong -- let me know and
> I'll send in a patch for wireguard instead.

I think ppp might be hit by the same bug, actually.
netdev_run_todo->ppp_dev_priv_destructor()->ppp_destroy_interface()->free_netdev(dev),
followed by "if (dev->needs_free_netdev)".