netdev - Re: [Patch net v2] mlx5: fixup checksum for short ethernet frame padding

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CANn89iKDNfUP4VzNMxNwKwO8+gyxZwKBr9nSFAeecripnGPYNw@mail.gmail.com>
Date:   Wed, 28 Nov 2018 15:50:35 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     netdev <netdev@...r.kernel.org>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: Re: [Patch net v2] mlx5: fixup checksum for short ethernet frame padding

On Wed, Nov 28, 2018 at 2:16 PM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> On Wed, Nov 28, 2018 at 7:00 AM Eric Dumazet <edumazet@...gle.com> wrote:
> >
> > Nice packet of death alert.
> >
> > pad_len can be 0xFFFFFF67  here, if frame_len is smaller than pad_offset.
>
> Unless IP header is malformed, how could it be?

This is totally something an attacker can forge.

ip_rcv_core()
...
len = ntohs(iph->tot_len);
if (skb->len < len) {
       __IP_INC_STATS(net, IPSTATS_MIB_INTRUNCATEDPKTS);
       goto drop;

No crash, but we drop and increment appropriate SNMP counter.