netdev - Re: KASAN: use-after-free Read in cfusbl_device

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Date:   Fri, 24 Jun 2022 08:32:31 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     "Dae R. Jeong" <threeearcat@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: KASAN: use-after-free Read in cfusbl_device_notify

On Fri, Jun 24, 2022 at 8:25 AM Dae R. Jeong <threeearcat@...il.com> wrote:
>
> On Fri, Jun 24, 2022 at 08:15:54AM +0200, Eric Dumazet wrote:
> > On Fri, Jun 24, 2022 at 8:08 AM Dae R. Jeong <threeearcat@...il.com> wrote:
> > >
> > > Hello,
> > >
> > > We observed a crash "KASAN: use-after-free Read in cfusbl_device_notify" during fuzzing.
> >
> > This is a known problem.
> >
> > Some drivers do not like NETDEV_UNREGISTER being delivered multiple times.
> >
> > Make sure in your fuzzing to have NET_DEV_REFCNT_TRACKER=y
> >
> > Thanks.
>
> Our config already have CONFIG_NET_DEV_REFCNT_TRACKER=y.

Are you also setting netdev_unregister_timeout_secs to a smaller value ?

netdev_unregister_timeout_secs
------------------------------

Unregister network device timeout in seconds.
This option controls the timeout (in seconds) used to issue a warning while
waiting for a network device refcount to drop to 0 during device
unregistration. A lower value may be useful during bisection to detect
a leaked reference faster. A larger value may be useful to prevent false
warnings on slow/loaded systems.
Default value is 10, minimum 1, maximum 3600.


> Anyway, this UAF report seems not interesting.
>
> Thank you for your quick reply.
>
>
> Best regards,
> Dae R. Jeong.