netdev - RE: [PATCH v9 2/2] lib: checksum: Use aligned accesses for ip_fast_csum and csum_ipv6

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]

Message-ID: <fa37be6a8c014d39ab75978e10995ca8@AcuMS.aculab.com>
Date: Fri, 23 Feb 2024 10:28:57 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Christophe Leroy' <christophe.leroy@...roup.eu>, Charlie Jenkins
	<charlie@...osinc.com>, Guenter Roeck <linux@...ck-us.net>, Palmer Dabbelt
	<palmer@...belt.com>, Andrew Morton <akpm@...ux-foundation.org>, Helge Deller
	<deller@....de>, "James E.J. Bottomley"
	<James.Bottomley@...senpartnership.com>, Parisc List
	<linux-parisc@...r.kernel.org>, Al Viro <viro@...iv.linux.org.uk>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: RE: [PATCH v9 2/2] lib: checksum: Use aligned accesses for
 ip_fast_csum and csum_ipv6_magic tests

From: Christophe Leroy
> Sent: 23 February 2024 10:07
...
> > +/* Ethernet headers are 14 bytes and NET_IP_ALIGN is used to align them */
> > +#define IP_ALIGNMENT (14 + NET_IP_ALIGN)
> 
> Only if no VLAN.
> 
> When using VLANs it is 4 bytes more. But why do you mind that at all ?

Wasn't one architecture faulting on a double-register read?
Where that had to be aligned (probably 8 bytes) but a normal
memory read could be misaligned?

I doubt it is valid to assume that the IP headers is 8 byte
aligned when NET_IP_ALIGN is 2.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)