[coreboot] When does AMD release the fam15 spectre microcode updates?

[Rudolf Marek]

Hi,

What do you want to protect? If you want to protect the kernel, retpolines are OK on AMD.
And you don't need any microcode update. Your CPU needs to have SMEP, otherwise
you would need to clear RSB on CPL change (the paper on mentined page says that you need to do that
always, but at least on Ryzen, the attack using RSB is not working (we tried that out, maybe it works
only on some circumstances).

If you want to protect userspace, the RSB will be clear by IBPB (which you would need if you don't have userspace compiled
with retpolines). I don't know if intel clears RSB on IBPB... probably not

To sum it up on AMD:

kernel:
retpolines, RSB clear on CPL change on CPU without SMEP (see above)

userspace:
retpolines, RSB clear on context switch necessary or IBPB (needs microcode update).

Plus make sure you enable "LFENCE is dispatch serializing" - perhaps coreboot can do that :) it is simple
MSR write on fam 10h 12h+ the fam 11h and 0fh dont have this MSR but LFENCE is dispatch serilizing.

Besides that, you don't need any microcode update.

Plus of course there is a spectre variant 1, which is more difficult to mitigate, basically you need to check all the software
and look for any pattern like array_x[array_z[untrusted_index] * any transformation].

The first access would leak just address (ASLR defated), second will leak data.
The variant 1 works on user/user attack and as well as user/kernel.

As far I know there are no automated tools to check for this.


Thanks
Rudolf









Dne 18.2.2018 v 12:48 Mike Banon napsal(a):
> Maybe its' a good idea to write to AMD support regarding this question
> - please share a reply if you would get an answer. I'm curious about
> other fam15 CPUs as well, e.g. A10-5750M microcode update would be
> nice, maybe a request could be more general, e.g. : what is the
> estimated release date for the microcode updates for fam15 AMD CPUs
> (so a request is  not about "opterons only")
> 
> On Sun, Feb 18, 2018 at 2:47 PM, Mike Banon <mikebdp2 at gmail.com> wrote:
>> Maybe its' a good idea to write to AMD support regarding this question
>> - please share a reply if you would get an answer. I'm curious about
>> other fam15 CPUs as well, e.g. A10-5750M microcode update would be
>> nice, maybe a request could be more general, e.g. : what is the
>> estimated release date for the microcode updates for fam15 AMD CPUs
>> (so a request is  not about "opterons only")
>>
>> On Sun, Feb 18, 2018 at 4:30 AM, Taiidan at gmx.com <Taiidan at gmx.com> wrote:
>>> They said they would be releasing opteron microcode updates in a few weeks
>>> but it has been over a month and I am wondering when this is going to happen
>>> or if it already has and I should re-compile coreboot?
>>>
>>> https://www.amd.com/en/corporate/speculative-execution
>>> "We expect to make updates available for our previous generation products
>>> over the coming weeks."
>>>
>>> Thanks!
>>>
>>>
>>> --
>>> coreboot mailing list: coreboot at coreboot.org
>>> https://mail.coreboot.org/mailman/listinfo/coreboot
>