netdev - Re: Double free of struct sk_buff reported by SLAB_CONSISTENCY_CHECKS with init_on

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Date:   Tue, 5 Nov 2019 11:19:08 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     Thibaut Sautereau <thibaut.sautereau@...p-os.org>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Networking <netdev@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Laura Abbott <labbott@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>, clipos@....gouv.fr
Subject: Re: Double free of struct sk_buff reported by SLAB_CONSISTENCY_CHECKS
 with init_on_free

On Tue, Nov 5, 2019 at 9:06 AM Thibaut Sautereau
<thibaut.sautereau@...p-os.org> wrote:
>
> On Mon, Nov 04, 2019 at 09:33:18AM -0800, Eric Dumazet wrote:
> >
> >
> > On 11/4/19 9:03 AM, Thibaut Sautereau wrote:
> > >
> > > We first encountered this issue under huge network traffic (system image
> > > download), and I was able to reproduce by simply sending a big packet
> > > with `ping -s 65507 <ip>`, which crashes the kernel every single time.
> > >
> >
> > Since you have a repro, could you start a bisection ?
>
> From my previous email:
>
>         "Bisection points to the following commit: 1b7e816fc80e ("mm: slub:
>         Fix slab walking for init_on_free"), and indeed the BUG is not
>         triggered when init_on_free is disabled."
>
> Or are you meaning something else?
Could you please give more specific reproduction steps?
I've checked out v5.3.8 from
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git, ran
`make defconfig` and added CONFIG_SLUB_DEBUG_ON=y.
Then I've built the kernel, ran it on QEMU with slub_debug=F and
init_on_free=1, SSHed into the machine and executed `ping -s 65507
127.0.0.1`
This however didn't trigger any crashes.
Am I missing something?
> --
> Thibaut Sautereau
> CLIP OS developer



-- 
Alexander Potapenko
Software Engineer

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