netdev - Re: [PATCH net] rtnetlink: Refine sanity checks in rtnl_fdb

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Date:   Fri, 30 Nov 2018 19:00:24 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        David Ahern <dsahern@...il.com>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        syzkaller@...glegroups.com, idosch@...lanox.com
Subject: Re: [PATCH net] rtnetlink: Refine sanity checks in rtnl_fdb_{add|del}

On Fri, Nov 30, 2018 at 08:17:04AM -0800, Eric Dumazet wrote:
> On Fri, Nov 30, 2018 at 8:10 AM Dmitry Vyukov <dvyukov@...gle.com> wrote:
> >
> > On Fri, Nov 30, 2018 at 4:02 PM, Ido Schimmel <idosch@...sch.org> wrote:
> > > On Fri, Nov 30, 2018 at 08:59:09AM -0700, David Ahern wrote:
> > >> This does not repro for me:
> > >> # ./a.out
> > >> Invalid address length 6 - must be 4 bytes
> > >> RTNETLINK answers: No buffer space available
> > >> RTNETLINK answers: Operation not supported
> > >> Invalid address length 6 - must be 4 bytes
> > >> Invalid address length 6 - must be 4 bytes
> > >> Invalid address length 6 - must be 4 bytes
> > >> Invalid address length 6 - must be 16 bytes
> > >> Invalid address length 6 - must be 16 bytes
> > >> Invalid address length 6 - must be 16 bytes
> > >>
> > >> config available>?
> > >
> > > You need a kernel with kmsan. See:
> > > https://github.com/google/kmsan
> >
> >
> > Another option may be to spray memory at the allocation stack with
> > some distinctive byte pattern and then check this pattern at the use
> > stack. Not 100% sounds, but should be enough for testing.
> 
> Well, no need for kmsan here, once you know the problem

Yes, agree. Patch is good. I'll tag your v2.

Thanks!