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Date: Wed, 12 Sep 2018 10:29:49 -0700
From: Kristen C Accardi <>
To: Eric Biggers <>
Subject: Re: [RFC PATCH] x86: entry: flush the cache if syscall error

On Tue, 2018-09-11 at 09:06 -0700, Eric Biggers wrote:
> On Mon, Sep 10, 2018 at 12:10:02PM -0700, Kristen Carlson Accardi
> wrote:
> > This patch aims to make it harder to perform cache timing attacks
> > on data
> > left behind by system calls. If we have an error returned from a
> > syscall,
> > flush the L1 cache.
> Which L1 cache?  There's no guarantee the task stayed on the same
> CPU...

While this is true, it is unlikely that the task switched CPUs for this
type of flow (i.e. an error path, presumably caught early-ish), and
worst case this would just mean we were wiping the wrong cache. I can
add a comment to indicate this scenario.

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