Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Wed, 6 Apr 2016 14:25:12 -0700
From: Kees Cook <>
To: Linus Torvalds <>, 
	"Rafael J. Wysocki" <>
Cc: Pavel Machek <>, Ard Biesheuvel <>, 
	Matt Redfearn <>, Yves-Alexis Perez <>, 
	Emrah Demir <>, Jonathan Corbet <>, 
	"the arch/x86 maintainers" <>, "Rafael J. Wysocki" <>, Len Brown <>, 
	Borislav Petkov <>, Andy Lutomirski <>, 
	"open list:DOCUMENTATION" <>, 
	"" <>, 
	Linux Kernel Mailing List <>, 
	"" <>
Subject: Re: [PATCH] Prefer kASLR over Hibernation

On Wed, Apr 6, 2016 at 1:56 PM, Linus Torvalds
<> wrote:
> On Wed, Apr 6, 2016 at 1:17 PM, Pavel Machek <> wrote:
>> Why is kASLR incompatible with hibernation? We can hibernate have
>> 4.3 kernel resume hibernation image of 4.2 kernel (on x86-64, and I
>> have patches for x86). Resuming kernel with different randomization
>> does not look that much different...
> Oh, I'd absolutely prefer to just allow kaslr together with
> hibernation if it actually works.
> Could the people who piped up to say that they actually use
> hibernation just try passing in the "kaslr" command line option on
> their machine, and see if it works for them? We could just remove the
> "no kaslr with hibername" code - or at least limit it to 32-bit for
> now..
> Because that would be lovely.

This is where our original investigation of having them coexist ended:

To quote Rafael Wysocki:
> We're jumping from the boot kernel into the image kernel.  The virtual address
> comes from the image kernel, but the boot kernel has to use it.  The only way
> we can ensure that we'll jump to the right place is to pass the physical address
> in the header (otherwise we de facto assume that the virtual address of the
> target page frame will be the same in both the boot and the image kernels).
> The missing piece is that the code in swsusp_arch_resume() sets up temporary
> page tables to ensure that they won't be overwritten while copying the last
> remaining image kernel pages to the right page frames (those page tables
> have to be stored in page frames that are free from the kernel image perspective).
> But if the kernel address space is randomized, set_up_temporary_mappings()
> really should duplicate the existing layout instead of creating a new one from
> scratch.  Otherwise, virtual addresses before set_up_temporary_mappings() may
> be different from the ones after it.


Kees Cook
Chrome OS & Brillo Security

Powered by blists - more mailing lists

Your e-mail address:

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.