From: "Woodhouse, David" <dwmw@amazon.co.uk>
To: "mail@maciej.szmigiero.name" <mail@maciej.szmigiero.name>,
"ak@linux.intel.com" <ak@linux.intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"tim.c.chen@linux.intel.com" <tim.c.chen@linux.intel.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"jpoimboe@redhat.com" <jpoimboe@redhat.com>,
"x86@kernel.org" <x86@kernel.org>,
"riel@redhat.com" <riel@redhat.com>,
"keescook@google.com" <keescook@google.com>,
"gnomes@lxorguk.ukuu.org.uk" <gnomes@lxorguk.ukuu.org.uk>,
"pjt@google.com" <pjt@google.com>,
"dave.hansen@intel.com" <dave.hansen@intel.com>,
"luto@amacapital.net" <luto@amacapital.net>,
"jikos@kernel.org" <jikos@kernel.org>,
"thomas.lendacky@amd.com" <thomas.lendacky@amd.com>,
"gregkh@linux-foundation.org" <gregkh@linux-foundation.org>
Subject: Re: x86/retpoline: Fill RSB on context switch for affected CPUs
Date: Fri, 9 Mar 2018 15:38:22 +0000 [thread overview]
Message-ID: <1520609785.17937.50.camel@amazon.co.uk> (raw)
In-Reply-To: <20180309151428.GE22087@tassilo.jf.intel.com>
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On Fri, 2018-03-09 at 07:14 -0800, Andi Kleen wrote:
> >
> > Shouldn't the RSB filling on context switch also be done on non-
> > IBPB
> > CPUs to protect (retpolined) user space tasks from other user space
> > tasks?
> The comment is actually incorrect. There's no risk to hit user space
> addresses if we have KPTI and NX (which is fairly universal).
... on non-AMD CPUS.
The comment does say "If we don't have SMEP or KPTI".
> It's mainly needed on Skylake era CPUs.
I wouldn't have added it if it were only for Skylake. We still have no
coherent overall mitigation for Skylake except the original IBRS setup.
Did anyone ever get any further with the call stack counting hacks?
Maciej, you might be right that to protect userspace processes from
each other we should also flush the RSB on context switch to a
"sensitive" process.
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prev parent reply other threads:[~2018-03-09 15:38 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-12 17:49 [PATCH] x86/retpoline: Fill RSB on context switch for affected CPUs David Woodhouse
2018-01-12 18:02 ` Andi Kleen
2018-01-12 18:23 ` David Woodhouse
2018-01-12 18:05 ` Andrew Cooper
2018-01-12 18:56 ` David Woodhouse
2018-01-12 23:41 ` Josh Poimboeuf
2018-01-14 11:39 ` Thomas Gleixner
2018-01-14 17:04 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-15 14:35 ` David Laight
2018-01-15 14:39 ` David Woodhouse
2018-01-15 14:42 ` Arjan van de Ven
2018-01-15 20:03 ` Kees Cook
2018-01-14 23:37 ` tip-bot for David Woodhouse
2018-01-15 0:05 ` Andi Kleen
2018-01-15 0:09 ` Andi Kleen
2018-01-15 10:13 ` David Woodhouse
2018-03-09 13:12 ` Maciej S. Szmigiero
2018-03-09 15:14 ` Andi Kleen
2018-03-09 15:33 ` Maciej S. Szmigiero
2018-03-09 15:38 ` Woodhouse, David [this message]
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