netdev - Re: [PATCH net v2 2/2] l2tp: fix races with ipv4-mapped ipv6 addresses

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Message-ID: <20180312171100.GG1351@alphalink.fr>
Date:   Mon, 12 Mar 2018 18:11:00 +0100
From:   Guillaume Nault <g.nault@...halink.fr>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        James Chapman <jchapman@...alix.com>,
        Wei Wang <weiwan@...gle.com>, David Ahern <dsahern@...il.com>
Subject: Re: [PATCH net v2 2/2] l2tp: fix races with ipv4-mapped ipv6
 addresses

On Mon, Mar 12, 2018 at 09:53:18AM +0100, Paolo Abeni wrote:
> On Fri, 2018-03-09 at 19:26 +0100, Guillaume Nault wrote:
> > On Fri, Mar 09, 2018 at 06:58:00PM +0100, Paolo Abeni wrote:
> > > The single threaded reproducer does not trigger anymore after 1/2,
> > > _but_ if ask syzbot to test 1/2 that will trigger another splat,
> > > because syzbot will do also multi threaded tests and we will hit the
> > > race between connect(tunnel->fd) and l2tp_tunnel_create(),
> > > 
> > 
> > Ok, and this case is handled by the sk_state test in l2tp_xmit_skb(),
> > right?
> 
> We need both such test and checking for v4mapped address in
> l2tp_xmit_skb()
> 
> > I just want to be sure that I didn't miss anything and that patch 1/2
> > combined with the socket state check in l2tp_xmit_skb() are enough to
> > fix the bug. And that overriding ->inet_*addr can be removed entirely
> > (and safely!).
> 
> I tested the above in vs the repro and in some real use case, but any
> additinal pair of eyes are welcome!
> 
It looks good to me too. I think everything is cleared up now.
Nice work!