linux-kernel - Re: Spectre mitigation doesn't seem to work at all?!

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Message-ID: <55e879f4-57c1-dc55-74ba-b1845cd5ded5@01019freenet.de>
Date:   Tue, 5 Jun 2018 07:53:24 +0200
From:   Andreas Hartmann <andihartmann@...19freenet.de>
To:     Alan Cox <gnomes@...rguk.ukuu.org.uk>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Spectre mitigation doesn't seem to work at all?!

On 06/04/2018 at 04:12 PM Alan Cox wrote:
>> A malicious program most probably won't care about that. Therefore, my
>> next question is: which memory regions can be exploited by a malicious
>> program? The complete physical memory or only the memory provided to the
>> malicious program? Should be the latter if this approach should have any
>> impact.
> 
> Spectre is not about memory regions. It's about speculative execution
> leaving measurable footprints. What footprints you leave depend upon what
> code you are executing. Thus the question becomes 'what can the target
> access'.
> 
> In order to attack something you need both a way to influence the code
> concerned and a way to measure it. In addition it needs to have some
> secret you want.
> 
> In practice that usually means something on the same system with its own
> memory space/privilege level. The usual cases then are user<->kernel and
> managed application<->runtime.

Would this be a practical test case: Gather keys and passwords used by a
ssh login by running a malicious program in parallel to sshd as another
ordinary user w/o root access.


Thanks,
Andreas