oss-sec mailing list archives
Re: AMD newest ucode 0x06000832 for Piledriver-based CPUs seems to behave in a problematic way
From: Robert Święcki <robert () swiecki net>
Date: Fri, 18 Mar 2016 15:28:11 +0100
2016-02-28 5:28 GMT+01:00 Robert Święcki <robert () swiecki 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
Current thread:
- AMD newest ucode 0x06000832 for Piledriver-based CPUs seems to behave in a problematic way Robert Święcki (Feb 27)
- Re: AMD newest ucode 0x06000832 for Piledriver-based CPUs seems to behave in a problematic way cve-assign (Feb 28)
- Re: AMD newest ucode 0x06000832 for Piledriver-based CPUs seems to behave in a problematic way Robert Święcki (Mar 18)