netdev - Re: [PATCH net] tcp: md5: fix potential overestimation of TCP option space

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Message-ID: <CACSApvb7Yz5xZjS=Qf8Sw1ftWGBU1Xn0+w8vrH1qjruv+PF-+Q@mail.gmail.com>
Date:   Fri, 6 Dec 2019 10:03:27 -0500
From:   Soheil Hassas Yeganeh <soheil@...gle.com>
To:     Neal Cardwell <ncardwell@...gle.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net] tcp: md5: fix potential overestimation of TCP option space

On Fri, Dec 6, 2019 at 9:49 AM Neal Cardwell <ncardwell@...gle.com> wrote:
>
> On Thu, Dec 5, 2019 at 1:10 PM Eric Dumazet <edumazet@...gle.com> wrote:
> >
> > Back in 2008, Adam Langley fixed the corner case of packets for flows
> > having all of the following options : MD5 TS SACK
> >
> > Since MD5 needs 20 bytes, and TS needs 12 bytes, no sack block
> > can be cooked from the remaining 8 bytes.
> >
> > tcp_established_options() correctly sets opts->num_sack_blocks
> > to zero, but returns 36 instead of 32.
> >
> > This means TCP cooks packets with 4 extra bytes at the end
> > of options, containing unitialized bytes.
> >
> > Fixes: 33ad798c924b ("tcp: options clean up")
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > Reported-by: syzbot <syzkaller@...glegroups.com>
> > ---
>
> Acked-by: Neal Cardwell <ncardwell@...gle.com>

Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>

Thanks for the fix!

> Thanks, Eric!
>
> neal