linux-kernel - Re: /sys/devices/system/cpu/vulnerabilities/ doesn't show all known CPU vulnerabilities

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Date:   Tue, 13 Aug 2019 23:21:15 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Kernel User <linux-kernel@...eup.net>
Cc:     linux-kernel@...r.kernel.org, mhocko@...e.com, x86@...nel.org
Subject: Re: /sys/devices/system/cpu/vulnerabilities/ doesn't show all known
 CPU vulnerabilities

On Tue, Aug 13, 2019 at 11:28:29PM +0300, Kernel User wrote:
> Hi,
> 
> 'ls /sys/devices/system/cpu/vulnerabilities/' doesn't show all known
> CPU vulnerabilities and their variants. Only some of them:
> 
> l1tf  mds  meltdown  spec_store_bypass  spectre_v1  spectre_v2
> 
> Wikipedia shows more variants:
> 
> https://en.wikipedia.org/wiki/Meltdown_(security_vulnerability)#Speculative_execution_security_vulnerabilities
> 
> It would be good to have a full list with statuses. Then one won't need to use external (potentially non-safe) tools like https://github.com/speed47/spectre-meltdown-checker to find out the vulnerabilities of a system.
> 

You have to consider that some of those are addressed by a single
mitigation like MDS; the mitigation for others like lazy FPU restore
is not even present in /sys/devices/system/cpu/vulnerabilities/. Also,
depending on the CPU, some are not even affected.

So maintaining this in the kernel is unnecessary to say the least.

We could use a writeup somewhere which maps each vulnerability name -
and they're a gazillion by now - to the respective mitigation and what
is required but I'm not aware of such a writeup.

Documentation/admin-guide/hw-vuln/ could be a good start and
Documentation/admin-guide/hw-vuln/mds.rst could be a good example how
one should document the vulnerabilities and their mitigation. But that
would need to be exhaustive.

IMHO of course.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.