From: Jiri Kosina <jikos@kernel.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Borislav Petkov <bp@suse.de>, David Woodhouse <dwmw@amazon.co.uk>,
Peter Zijlstra <peterz@infradead.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] x86/bugs: protect against userspace-userspace spectreRSB
Date: Wed, 25 Jul 2018 15:50:44 +0200 (CEST) [thread overview]
Message-ID: <nycvar.YFH.7.76.1807251547550.997@cbobk.fhfr.pm> (raw)
In-Reply-To: <20180725134512.uquatm2neqr5jy7b@treble>
On Wed, 25 Jul 2018, Josh Poimboeuf wrote:
> > The article "Spectre Returns! Speculation Attacks using the Return Stack
> > Buffer" [1] describes two new (sub-)variants of spectrev2-like attack,
> > making use solely of the RSB contents even on CPUs that don't fallback to
> > BTB on RSB underflow (Skylake+).
> >
> > Mitigate userspace-userspace attacks by always unconditionally filling RSB on
> > context switch when generic spectrev2 mitigation has been enabled.
> >
> > [1] https://arxiv.org/pdf/1807.07940.pdf
> >
> > Signed-off-by: Jiri Kosina <jkosina@suse.cz>
>
> While I generally agree with this patch, isn't it odd that we would do
> RSB filling on every context switch, but almost never do IBPB?
Yeah, I have actually been wondering exactly the same, but that's what we
have been doing so far on SKL+, so I didn't really want to mix this aspect
in.
I actually believe that in the name of consistency we should've been doing
the RSB fills under the same conditions we're issuing IBPB even on SKL+; I
can resend a patch that re-adjusts that, if that's the consensus.
Thanks,
--
Jiri Kosina
SUSE Labs
next prev parent reply other threads:[~2018-07-25 13:50 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-24 19:53 [PATCH] x86/bugs: protect against userspace-userspace spectreRSB Jiri Kosina
2018-07-25 13:45 ` Josh Poimboeuf
2018-07-25 13:50 ` Jiri Kosina [this message]
2018-07-25 17:11 ` Josh Poimboeuf
2018-07-30 17:59 ` Tim Chen
2018-07-25 17:28 ` Linus Torvalds
2018-07-25 23:11 ` Jiri Kosina
2018-07-25 23:27 ` Josh Poimboeuf
2018-07-26 11:14 ` [PATCH v2] " Jiri Kosina
2018-07-30 17:56 ` Tim Chen
2018-07-30 19:13 ` Konrad Rzeszutek Wilk
2018-07-30 22:48 ` [tip:x86/pti] x86/speculation: Protect " tip-bot for Jiri Kosina
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