From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
David Kaplan <David.Kaplan@amd.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
David Woodhouse <dwmw2@infradead.org>,
Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>
Subject: Re: Do we need to do anything about "dead µops?"
Date: Mon, 3 May 2021 18:30:10 -0500 [thread overview]
Message-ID: <20210503233010.x5lzpw4dq3gueg47@treble> (raw)
In-Reply-To: <CALCETrXRvhqw0fibE6qom3sDJ+nOa_aEJQeuAjPofh=8h1Cujg@mail.gmail.com>
On Sat, May 01, 2021 at 09:26:33AM -0700, Andy Lutomirski wrote:
> Hi all-
>
> The "I See Dead µops" paper that is all over the Internet right now is
> interesting, and I think we should discuss the extent to which we
> should do anything about it. I think there are two separate issues:
>
> First, should we (try to) flush the µop cache across privilege
> boundaries? I suspect we could find ways to do this, but I don't
> really see the point. A sufficiently capable attacker (i.e. one who
> can execute their own code in the dangerous speculative window or one
> who can find a capable enough string of gadgets) can put secrets into
> the TLB, various cache levels, etc. The µop cache is a nice piece of
> analysis, but I don't think it's qualitatively different from anything
> else that we don't flush. Am I wrong?
Wouldn't this type of gadget (half-v1 gadget + value-dependent-branch)
would be much more likely to occur than a traditional Spectre v1
(half-v1 gadget + value-addressed-load)?
Also, in section V.A., they identified 37 gadgets. Has anybody looked
at those yet?
(And this makes me realize my uaccess pointer masking patch [1] never
got merged...)
[1] https://lore.kernel.org/lkml/1d06ed6485b66b9f674900368b63d7ef79f666ca.1599756789.git.jpoimboe@redhat.com/
--
Josh
next prev parent reply other threads:[~2021-05-03 23:30 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-01 16:26 Do we need to do anything about "dead µops?" Andy Lutomirski
2021-05-01 17:35 ` Andrew Cooper
2021-05-03 23:30 ` Josh Poimboeuf [this message]
2021-05-04 1:31 ` Andy Lutomirski
2021-05-04 3:16 ` Josh Poimboeuf
2021-05-04 13:06 ` David Laight
2021-05-04 13:24 ` Josh Poimboeuf
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