From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Jiri Kosina <jikos@kernel.org>
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 08:45:12 -0500 [thread overview]
Message-ID: <20180725134512.uquatm2neqr5jy7b@treble> (raw)
In-Reply-To: <nycvar.YFH.7.76.1807242147560.997@cbobk.fhfr.pm>
On Tue, Jul 24, 2018 at 09:53:30PM +0200, Jiri Kosina wrote:
> From: Jiri Kosina <jkosina@suse.cz>
>
> 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?
> + * - RSB underflow (and switch to BTB) on Skylake+
> + * - sepctreRSB variant of spectre v2 on X86_BUG_SPECTRE_V2 CPUs
"SpectreRSB"
> */
> - if ((!boot_cpu_has(X86_FEATURE_PTI) &&
> - !boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) {
> - setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
> - pr_info("Spectre v2 mitigation: Filling RSB on context switch\n");
> - }
> + setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
> + pr_info("Spectre v2 / spectreRSB mitigation: Filling RSB on context switch\n");
"SpectreRSB" (capitalized)
--
Josh
next prev parent reply other threads:[~2018-07-25 13:45 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 [this message]
2018-07-25 13:50 ` Jiri Kosina
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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