From: Liran Alon <liran.alon@oracle.com>
To: <dave.hansen@intel.com>
Cc: <labbott@redhat.com>, <luto@kernel.org>,
<Janakarajan.Natarajan@amd.com>, <torvalds@linux-foundation.org>,
<bp@suse.de>, <asit.k.mallick@intel.com>, <rkrcmar@redhat.com>,
<karahmed@amazon.de>, <hpa@zytor.com>, <mingo@redhat.com>,
<jun.nakajima@intel.com>, <x86@kernel.org>, <ashok.raj@intel.com>,
<arjan.van.de.ven@intel.com>, <tim.c.chen@linux.intel.com>,
<pbonzini@redhat.com>, <ak@linux.intel.com>,
<linux-kernel@vger.kernel.org>, <dwmw2@infradead.org>,
<peterz@infradead.org>, <tglx@linutronix.de>,
<gregkh@linuxfoundation.org>, <mhiramat@kernel.org>,
<arjan@linux.intel.com>, <thomas.lendacky@amd.com>,
<dan.j.williams@intel.com>, <joro@8bytes.org>,
<kvm@vger.kernel.org>, <aarcange@redhat.com>
Subject: Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation
Date: Thu, 25 Jan 2018 18:50:27 -0800 (PST) [thread overview]
Message-ID: <23aae227-461c-4d0d-8ccb-df01bae98b2e@default> (raw)
----- dave.hansen@intel.com wrote:
> On 01/25/2018 06:11 PM, Liran Alon wrote:
> > It is true that attacker cannot speculate to a kernel-address, but
> it
> > doesn't mean it cannot use the leaked kernel-address together with
> > another unrelated vulnerability to build a reliable exploit.
>
> The address doesn't leak if you can't execute there. It's the same
> reason that we don't worry about speculation to user addresses from
> the
> kernel when SMEP is in play.
Maybe I misunderstand BTB & BHB internals. Will be glad if you could pinpoint my error.
Google P0 blog-post (https://googleprojectzero.blogspot.co.il/2018/01/reading-privileged-memory-with-side.html) claims that BTB & BHB only use <31 low bits of the address of the source instruction to lookup into the BTB. In addition, it claims that the higher bits of the predicated destination change together with the higher bits of the source instruction.
Therefore, it should be possible to leak the low bits of high predicition-mode code BTB/BHB entries from low prediction-mode code. Because the predicted destination address will reside in user-space.
What am I missing?
Thanks,
-Liran
next reply other threads:[~2018-01-26 2:50 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-26 2:50 Liran Alon [this message]
2018-01-26 2:55 ` [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation Van De Ven, Arjan
-- strict thread matches above, loose matches on Subject: below --
2018-01-26 2:11 Liran Alon
2018-01-26 2:23 ` Dave Hansen
2018-01-26 9:11 ` David Woodhouse
2018-01-26 17:19 ` Linus Torvalds
2018-01-26 17:27 ` Borislav Petkov
2018-01-26 17:29 ` David Woodhouse
2018-01-26 17:31 ` David Woodhouse
2018-01-26 17:59 ` Andi Kleen
2018-01-26 18:11 ` David Woodhouse
2018-01-26 18:12 ` Arjan van de Ven
2018-01-26 18:26 ` David Woodhouse
2018-01-26 18:28 ` Van De Ven, Arjan
2018-01-26 18:43 ` David Woodhouse
2018-01-26 18:44 ` Van De Ven, Arjan
2018-01-26 18:53 ` David Woodhouse
2018-01-26 19:02 ` Konrad Rzeszutek Wilk
2018-01-26 19:11 ` Hansen, Dave
2018-01-27 13:42 ` Konrad Rzeszutek Wilk
2018-01-27 15:55 ` Dave Hansen
2018-01-26 19:11 ` David Woodhouse
2018-01-26 8:46 ` David Woodhouse
2018-01-23 11:13 Liran Alon
2018-01-25 22:20 ` Dave Hansen
2018-01-22 22:15 Luke Kenneth Casson Leighton
2018-01-20 19:22 [RFC 00/10] Speculation Control feature support KarimAllah Ahmed
2018-01-20 19:23 ` [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation KarimAllah Ahmed
2018-01-21 19:14 ` Andy Lutomirski
2018-01-23 16:12 ` Tom Lendacky
2018-01-23 16:20 ` Woodhouse, David
2018-01-23 22:37 ` Tom Lendacky
2018-01-23 22:49 ` Andi Kleen
2018-01-23 23:14 ` Woodhouse, David
2018-01-23 23:22 ` Andi Kleen
2018-01-24 0:47 ` Tim Chen
2018-01-24 1:00 ` Andy Lutomirski
2018-01-24 1:22 ` David Woodhouse
2018-01-24 1:59 ` Van De Ven, Arjan
2018-01-24 3:25 ` Andy Lutomirski
2018-01-21 19:34 ` Linus Torvalds
2018-01-21 20:28 ` David Woodhouse
2018-01-21 21:35 ` Linus Torvalds
2018-01-21 22:00 ` David Woodhouse
2018-01-21 22:27 ` Linus Torvalds
2018-01-22 16:27 ` David Woodhouse
2018-01-23 7:29 ` Ingo Molnar
2018-01-23 7:53 ` Ingo Molnar
2018-01-23 9:27 ` Ingo Molnar
2018-01-23 9:37 ` David Woodhouse
2018-01-23 15:01 ` Dave Hansen
2018-01-23 9:30 ` David Woodhouse
2018-01-23 10:15 ` Ingo Molnar
2018-01-23 10:27 ` David Woodhouse
2018-01-23 10:44 ` Ingo Molnar
2018-01-23 10:57 ` David Woodhouse
2018-01-23 10:23 ` Ingo Molnar
2018-01-23 10:35 ` David Woodhouse
2018-02-04 18:43 ` Thomas Gleixner
2018-02-04 20:22 ` David Woodhouse
2018-02-06 9:14 ` David Woodhouse
2018-01-25 16:19 ` Mason
2018-01-25 17:16 ` Greg Kroah-Hartman
2018-01-29 11:59 ` Mason
2018-01-24 0:05 ` Andi Kleen
2018-01-23 20:16 ` Pavel Machek
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