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  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:   Wed, 30 Dec 2020 18:13:15 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Pali Rohár <pali@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Marek Behún <kabel@...nel.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] net: sfp: add workaround for Realtek RTL8672 and
 RTL9601C chips

On Wed, Dec 30, 2020 at 05:05:46PM +0000, Russell King - ARM Linux admin wrote:
> On Wed, Dec 30, 2020 at 05:56:34PM +0100, Pali Rohár wrote:
> > This change is really required for those Realtek chips. I thought that
> > it is obvious that from *both* addresses 0x50 and 0x51 can be read only
> > one byte at the same time. Reading 2 bytes (for be16 value) cannot be
> > really done by one i2 transfer, it must be done in two.
> 
> Then these modules are even more broken than first throught, and
> quite simply it is pointless supporting the diagnostics on them
> because we can never read the values in an atomic way.
> 
> It's also a violation of the SFF-8472 that _requires_ multi-byte reads
> to read these 16 byte values atomically. Reading them with individual
> byte reads results in a non-atomic read, and the 16-bit value can not
> be trusted to be correct.

Hi Pali

I have to agree with Russell here. I would rather have no diagnostics
than untrustable diagnostics.

The only way this is going to be accepted is if the manufacture says
that reading the first byte of a word snapshots the second byte as
well in an atomic way and returns that snapshot on the second
read. But i highly doubt that happens, given how bad these SFPs are.

      Andrew

Powered by blists - more mailing lists