From: Eric Biggers <ebiggers@kernel.org>
To: Kristen C Accardi <kristen@linux.intel.com>
Cc: kernel-hardening@lists.openwall.com
Subject: Re: [RFC PATCH] x86: entry: flush the cache if syscall error
Date: Wed, 12 Sep 2018 10:45:58 -0700 [thread overview]
Message-ID: <20180912174540.GA222557@gmail.com> (raw)
In-Reply-To: <1536773389.3240.4.camel@linux.intel.com>
On Wed, Sep 12, 2018 at 10:29:49AM -0700, Kristen C Accardi wrote:
> 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),
How you do know it's unlikely? What degrees of freedom might an attacker have
in controlling this?
> worst case this would just mean we were wiping the wrong cache. I can
> add a comment to indicate this scenario.
>
IOW, the protection may be useless?
- Eric
next prev parent reply other threads:[~2018-09-12 17:45 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-10 19:10 [RFC PATCH] x86: entry: flush the cache if syscall error Kristen Carlson Accardi
2018-09-10 20:32 ` Jann Horn
2018-09-11 15:58 ` Kristen C Accardi
2018-09-11 16:12 ` Jann Horn
2018-09-11 8:41 ` Greg KH
2018-09-11 16:01 ` Kristen C Accardi
2018-09-11 16:06 ` Eric Biggers
2018-09-12 17:29 ` Kristen C Accardi
2018-09-12 17:45 ` Eric Biggers [this message]
2018-09-12 18:19 ` Rik van Riel
2018-09-11 18:02 ` Jann Horn
2018-09-12 17:34 ` Kristen C Accardi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180912174540.GA222557@gmail.com \
--to=ebiggers@kernel.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=kristen@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.