linux-kernel - Re: [PATCH RFC] net/macb: Fix UDPv4 checksum offload

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:	Tue, 28 Apr 2015 15:36:54 -0500
From:	Jaeden Amero <jaeden.amero@...com>
To:	David Miller <davem@...emloft.net>
CC:	nicolas.ferre@...el.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, jeff.westfahl@...com,
	mihai.neagu@...com
Subject: Re: [PATCH RFC] net/macb: Fix UDPv4 checksum offload

On 04/27/2015 09:47 PM, David Miller wrote:
> From: Jaeden Amero <jaeden.amero@...com>
> Date: Mon, 27 Apr 2015 17:43:30 -0500
>
> A UDP checksum of zero, means "checksum not computed".  And your
> device isn't computing the checksum at all, but rather is leaving it
> at zero.

The "zero" checksum is not what gets sent over the wire. Independent of
the value of the checksum field, hardware generates a correct checksum
for payloads of 3 or more bytes. The bug is that hardware generates an
incorrect checksum for payloads of 2 or less bytes, unless the checksum
field is zeroed.

> You need to handle this properly by computing the checksum in
> software and then setting the TX descriptor bits such that the
> chip leaves the checksum field alone.

Unfortunately, the Cadence MACB doesn't support the enabling or
disabling of checksum generation per descriptor.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/