Re: [kernel-hardening] [RFC] x86, mm: start mmap allocation for libs from low addresses

[Solar Designer <solar@openwall.com>]

On Mon, Sep 05, 2011 at 04:46:47PM +0400, Vasiliy Kulikov wrote:
> Hmm, yes, looks like I've lost the thread some time ago :(  A good
> description definitely needs much longer and scrupulous analysis.

Or alternatively it may choose not to go into detail at all, which is a
safer bet. ;-)

> Probably there is a public paper with a review/analysis/benefits of
> ASCII-armor that we're able to refer in the patch description?  I cannot
> find any rigorous paper, unfortunately.

I'm not aware of such paper.

> On Sun, Sep 04, 2011 at 03:57 +0400, Solar Designer wrote:
> > solar@host:~/kernel/mainline/linux-3.0.4 $ fgrep -rl CONFIG_VM86 .
> > ./arch/x86/kernel/Makefile
> > ./arch/x86/kernel/entry_32.S
> > ./arch/x86/include/asm/vm86.h
> > ./arch/x86/include/asm/processor-flags.h
> > 
> > Looks like there's no Kconfig option for this - perhaps add it with a
> > separate patch?
> 
> Since 2.6.x CONFIG_ prefix is not used in Kconfig files:
> 
> $ grep -w VM86 arch/x86/Kconfig
> config VM86
>     bool "Enable VM86 support" if EXPERT

Oh, of course.  Sometimes I say/do dumb things.

Turns out this stuff is also present in RHEL5/OpenVZ kernels, so we
might want to turn on CONFIG_EMBEDDED and disable CONFIG_VM86 in Owl
kernel builds, even before we move to newer kernels.

Alexander