netdev - Re: KASAN poisoning for skb linear data

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Date:   Thu, 8 Mar 2018 07:45:43 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     David Miller <davem@...emloft.net>,
        Willem de Bruijn <willemb@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        andreyknvl <andreyknvl@...gle.com>
Subject: Re: KASAN poisoning for skb linear data

On Mon, 15 Jan 2018 15:15:04 +0100
Dmitry Vyukov <dvyukov@...gle.com> wrote:

> Hi,
> 
> As far as I understand pskb_may_pull() plays important role in packet
> parsing for all protocols. And we did custom fragmentation of packets
> emitted via tun (IFF_NAPI_FRAGS). However, it seems that it does not
> give any results (bugs found), and I think the reason for this is that
> linear data is rounded up and is usually quite large. So if a parsing
> function does pskb_may_pull(1), or does not do it at all, it can
> usually access more and it will go unnoticed. KASAN has an ability to
> do custom poisoning: it can poison/unpoison any memory range, and then
> detect any reads/writes to that range. What do you think about adding
> custom KASAN poisoning to pskb_may_pull() and switching it to
> non-eager mode (pull only what was requested) under KASAN? Do you
> think it has potential for finding important bugs? What amount of work
> is this?
> 
> Thanks

Also, kernel networking only deals with in-tree upstream code.
Any problems with infrastructure for custom code are your problem
to deal with, not our problem.