netdev - Re: [PATCH v3 net-next 2/3] openvswitch: Use is_skb

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:   Fri, 2 Dec 2016 10:25:09 +0100
From:   Jiri Benc <jbenc@...hat.com>
To:     Pravin Shelar <pshelar@....org>
Cc:     Jarno Rajahalme <jarno@....org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Eric Garver <e@...g.me>
Subject: Re: [PATCH v3 net-next 2/3] openvswitch: Use is_skb_forwardable()
 for length check.

On Thu, 1 Dec 2016 11:50:00 -0800, Pravin Shelar wrote:
> This is not changing any behavior compared to current OVS vlan checks.
> Single vlan header is not considered for MTU check.

It is changing it.

Consider the case when there's an interface with MTU 1500 forwarding to
an interface with MTU 1496. Obviously, full-sized vlan frames
ingressing on the first interface are not forwardable to the second
one. Yet, if the vlan tag is accelerated (and thus not counted in
skb->len), is_skb_forwardable happily returns true because of the check

        len = dev->mtu + dev->hard_header_len + VLAN_HLEN;
        if (skb->len <= len)

 Jiri