netdev - Re: [Patch net] mlx5: check for malformed packets

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Message-ID: <CALzJLG9EhopwN2TwWLBd8cKgZrPYBgaQBMvZ_a6=RtNkpp74=w@mail.gmail.com>
Date:   Tue, 4 Dec 2018 11:32:48 -0800
From:   Saeed Mahameed <saeedm@....mellanox.co.il>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Linux Netdev List <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: Re: [Patch net] mlx5: check for malformed packets

On Sat, Dec 1, 2018 at 12:38 PM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> is_last_ethertype_ip() is used to check IP/IPv6 protocol before
> parsing IP/IPv6 headers.
>
> But __vlan_get_protocol() is only bound to skb->len, a malicious
> packet could exhaust all skb->len by inserting sufficient ETH_P_8021AD
> headers, and it may not even contain an IP/IPv6 header at all, so we
> have to check if we are still safe to continue to parse IP/IPv6 header.
> If not, treat it as non-IP packet.
>
> This should not cause any crash as we stil have tail room in skb,
> but we can't just rely on it either.

Hi Cong, is this reproducible or just a theory ? which part of the
code you think will cause the invalid access or crash ?
do you have steps to reproduce this?

I would like to investigate this myself, it will take a couple of days
if that's ok with you ..

Thanks,
Saeed.