linux-kernel - Re: [PATCH] x86/kconfig/32: Mark CONFIG

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Date:	Tue, 07 Jul 2015 19:33:34 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Andy Lutomirski <luto@...nel.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
CC:	Oleg Nesterov <oleg@...hat.com>, Kees Cook <keescook@...omium.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] x86/kconfig/32: Mark CONFIG_VM86 as BROKEN

On 7/7/2015 6:25 PM, Andy Lutomirski wrote:
> VM86 is entirely broken if ptrace, syscall auditing, or NOHZ_FULL is
> in use.  The code is a big undocumented mess, it's a real PITA to
> test, and it looks like a big chunk of vm86_32.c is dead code.  It
> also plays awful games with the entry asm.
>
> No one should be using it anyway.  Use DOSBOX or KVM instead.
>
> Mark it BROKEN.  I want to remove some (obviously incorrect) exit
> asm that it depends on, and I don't want to figure out how to run
> severely obsolete programs just to test something that no one uses
> for anything other than exploits anyway.
>

while it is never great to deprecate features, in this case I am not sure
there is another choice unless someone steps up to seriously revamp this code.
(and look at it from a PREEMPT, NO_HZ etc etc angle)

if this patch would not be acceptable, at minimum we need some sort of "off by default
unless the sysadmin flips a sysfs thing", which is really just a huge hack.


so for me this is

Acked-by: Arjan van de Ven <arjan@...ux.intel.com>


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