From: "Woodhouse, David" <dwmw@amazon.co.uk>
To: "torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
"ak@linux.intel.com" <ak@linux.intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"peterz@infradead.org" <peterz@infradead.org>,
"tim.c.chen@linux.intel.com" <tim.c.chen@linux.intel.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"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>,
"gregkh@linux-foundation.org" <gregkh@linux-foundation.org>
Subject: Re: [PATCH v6 11/10] x86/retpoline: Avoid return buffer underflows on context switch
Date: Tue, 9 Jan 2018 01:18:30 +0000 [thread overview]
Message-ID: <1515460709.4423.101.camel@amazon.co.uk> (raw)
In-Reply-To: <CA+55aFy3sCY5xUwZtOYL1MLhRwYe1sU=5d8sWPZqAnEZ71u8-w@mail.gmail.com>
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On Mon, 2018-01-08 at 16:58 -0800, Linus Torvalds wrote:
>
> And THAT is where "clear the registers" comes in. It adds _another_
> huge barrier to an attack that was already pretty hard to begin with.
>
> If we clear the registers, what the hell are you going to put in the
> RSB that helps you?
As you go back up the call stack, a lot of caller-saved registers are
going to end up being reloaded, before you hit the mispredicted 'ret'.
Much of those could be attacker-controlled, by data passed in to the
syscall or pre-populated in other data structures.
Clearing the call-clobbered registers in context switch will probably
eliminate a few attack vectors, but I'm not sure it's even the
majority.
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next prev parent reply other threads:[~2018-01-09 1:18 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-07 22:11 [PATCH v6 00/10] Retpoline: Avoid speculative indirect calls in kernel David Woodhouse
2018-01-07 22:11 ` [PATCH v6 01/10] x86/retpoline: Add initial retpoline support David Woodhouse
2018-01-08 10:45 ` Peter Zijlstra
2018-01-08 10:53 ` David Woodhouse
2018-01-08 11:03 ` Peter Zijlstra
2018-01-08 12:45 ` David Woodhouse
2018-01-08 13:42 ` Josh Poimboeuf
2018-01-08 13:46 ` Thomas Gleixner
2018-01-08 13:53 ` Josh Poimboeuf
2018-01-08 14:26 ` David Woodhouse
2018-01-08 21:20 ` Josh Poimboeuf
2018-01-09 12:36 ` Peter Zijlstra
2018-01-09 13:35 ` Thomas Gleixner
2018-01-09 13:40 ` Woodhouse, David
2018-01-07 22:11 ` [PATCH v6 02/10] x86/retpoline/crypto: Convert crypto assembler indirect jumps David Woodhouse
2018-01-08 13:49 ` Josh Poimboeuf
2018-01-07 22:11 ` [PATCH v6 03/10] x86/retpoline/entry: Convert entry " David Woodhouse
2018-01-07 22:11 ` [PATCH v6 04/10] x86/retpoline/ftrace: Convert ftrace " David Woodhouse
2018-01-07 22:11 ` [PATCH v6 05/10] x86/retpoline/hyperv: Convert " David Woodhouse
2018-01-07 22:11 ` [PATCH v6 06/10] x86/retpoline/xen: Convert Xen hypercall " David Woodhouse
2018-01-07 22:11 ` [PATCH v6 07/10] x86/retpoline/checksum32: Convert assembler " David Woodhouse
2018-01-07 22:11 ` [PATCH v6 08/10] x86/retpoline/irq32: " David Woodhouse
2018-01-07 22:11 ` [PATCH v6 09/10] x86/retpoline: Add boot time option to disable retpoline David Woodhouse
2018-01-07 22:11 ` [PATCH v6 10/10] x86/retpoline: Exclude objtool with retpoline David Woodhouse
2018-01-08 10:25 ` Thomas Gleixner
2018-01-08 10:34 ` Woodhouse, David
2018-01-08 13:20 ` Josh Poimboeuf
2018-01-07 22:22 ` [PATCH v6 00/10] Retpoline: Avoid speculative indirect calls in kernel Linus Torvalds
2018-01-08 10:01 ` Thomas Gleixner
2018-01-08 17:54 ` Ingo Molnar
2018-01-08 21:10 ` Thomas Gleixner
2018-01-08 10:34 ` Paul Turner
2018-01-08 10:38 ` Jiri Kosina
2018-01-08 10:45 ` Paul Turner
2018-01-08 10:42 ` Paul Turner
2018-01-08 11:16 ` Andrew Cooper
2018-01-08 11:25 ` Paul Turner
2018-01-08 16:13 ` Alexei Starovoitov
2018-01-10 15:20 ` Woodhouse, David
2018-01-10 15:31 ` Dr. David Alan Gilbert
2018-01-08 10:45 ` David Woodhouse
2018-01-08 10:53 ` Paul Turner
2018-01-08 12:49 ` David Woodhouse
2018-01-08 23:44 ` [PATCH v6 11/10] x86/retpoline: Avoid return buffer underflows on context switch David Woodhouse
2018-01-08 23:56 ` Linus Torvalds
2018-01-08 23:58 ` Woodhouse, David
2018-01-09 0:35 ` Linus Torvalds
2018-01-09 0:42 ` David Woodhouse
2018-01-09 0:48 ` Linus Torvalds
2018-01-09 0:55 ` David Woodhouse
2018-01-09 0:44 ` Andi Kleen
2018-01-09 0:58 ` Linus Torvalds
2018-01-09 1:15 ` Andrew Cooper
2018-01-09 3:27 ` Andy Lutomirski
2018-01-09 13:04 ` David Woodhouse
2018-01-09 13:10 ` Peter Zijlstra
2018-01-09 17:53 ` Kees Cook
2018-01-09 18:09 ` Linus Torvalds
2018-02-16 8:58 ` Pavel Machek
2018-01-09 1:16 ` Andi Kleen
2018-01-09 1:21 ` [PATCH v6 11/10] x86/retpoline: Avoid return buffer underflows on context switch II Andi Kleen
2018-01-09 1:23 ` Woodhouse, David
2018-01-09 1:49 ` Andi Kleen
2018-01-09 1:53 ` Paul Turner
2018-01-09 1:18 ` Woodhouse, David [this message]
2018-01-09 0:06 ` [PATCH v6 11/10] x86/retpoline: Avoid return buffer underflows on context switch Andi Kleen
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