netdev - Re: [PATCH net] ipv6: fix out-of-bound access in ip6_parse

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Message-ID: <CANn89i+c5QhVt4NDtvx6ap8HdPyJKVtrpXyhdAMqRWBLZBzApw@mail.gmail.com>
Date:   Thu, 24 Jun 2021 12:08:05 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        Tom Herbert <tom@...bertland.com>
Subject: Re: [PATCH net] ipv6: fix out-of-bound access in ip6_parse_tlv()

On Thu, Jun 24, 2021 at 11:49 AM Paolo Abeni <pabeni@...hat.com> wrote:
>
> On Wed, 2021-06-23 at 12:43 -0700, Eric Dumazet wrote:
> > From: Eric Dumazet <edumazet@...gle.com>
> >
> > First problem is that optlen is fetched without checking
> > there is more than one byte to parse.
> >
> > Fix this by taking care of IPV6_TLV_PAD1 before
> > fetching optlen (under appropriate sanity checks against len)
> >
> > Second problem is that IPV6_TLV_PADN checks of zero
> > padding are performed before the check of remaining length.
> >
> > Fixes: c1412fce7ecc ("net/ipv6/exthdrs.c: Strict PadN option checking")
>
> Perhaps even:
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>
> for the first issue?
>

> +             if (nh[off] == IPV6_TLV_PAD1) {
> >                       optlen = 1;
>
> It looks like the above assignment is not needed anymore.
>
> Other than that LGTM,
>

Thanks for the review, I am sending the v2.