Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Fri, 18 Mar 2016 15:28:11 +0100
From: Robert Święcki <robert@...ecki.net>
To: oss-security@...ts.openwall.com
Subject: Re: AMD newest ucode 0x06000832 for Piledriver-based CPUs seems to
 behave in a problematic way

2016-02-28 5:28 GMT+01:00 Robert Święcki <robert@...ecki.net>:

> AMD newest public ucode 0x06000832 for Piledriver-based CPUs (newer
> AMD FX, and Opteron 3300/4300/6300 series) seems to be broken. Under
> certain conditions it allows unprivileged users running under qemu VMs
> to affect the host Linux kernel in a problematic manner: the CPU
> starts to behave in an erratic way, and it leads to CPU execution flow
> of the host kernel (the one running on bare metal) to be changed.

It seems that AMD (somewhat silently) released - in
https://lkml.org/lkml/2016/3/17/43 - a new microcode for 15th family
of AMD CPUs.

I applied this patch to the previous ucode, and got this -
http://alt.swiecki.net/.a/amd-ucode-20160316.tbz2 - which resulted in:

[1634167.526985] microcode: CPU0: new patch_level=0x0600084f
[1634167.560059] microcode: CPU2: new patch_level=0x0600084f
[1634167.584795] microcode: CPU4: new patch_level=0x0600084f
[1634167.609298] microcode: CPU6: new patch_level=0x0600084f

Quick testing suggests that bugs from 0x06000832 and 0x06000836 ucode
versions are gone. Unfortunately it's not published yet on
http://www.amd64.org/microcode.html nor the new README/errata is
available, so I have no more details on that, but given that AMD
promised new ucode in March fixing this problem - as per
http://www.theregister.co.uk/2016/03/06/amd_microcode_6000836_fix/ -
this might be it.

-- 
Robert Święcki

Powered by blists - more mailing lists

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.