netdev - Re: [net PATCH] flow_dissector: Fix unaligned access in __skb_flow_dissector when used by eth_get

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:	Sat, 30 Jan 2016 11:26:51 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Alexander Duyck <alexander.duyck@...il.com>
Cc:	Sowmini Varadhan <sowmini.varadhan@...cle.com>,
	Alexander Duyck <aduyck@...antis.com>,
	Netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Tom Herbert <tom@...bertland.com>
Subject: Re: [net PATCH] flow_dissector: Fix unaligned access in
 __skb_flow_dissector when used by eth_get_headlen

On Sat, 2016-01-30 at 10:36 -0800, Alexander Duyck wrote:

> As far as the NET_IP_ALIGN on the page offset I think it is a horrible
> idea.  Basically it means we have to allocate at least 1K more space
> than we need since page sizes are powers of 2, and buffer sizes in
> hardware are measured in 1K increments.

I thought Ethernet frames were something like ~1500 bytes.

Can't you program the NIC to not receive frames bigger than MTU + 18, or
at least 2046 ?

Of course, if the NIC is able to push 2048 bytes (instead of 2046 max),
using an offset of 2 is not going to work.