Message-ID: <559C8BFE.6050604@linux.intel.com>
Date: Tue, 07 Jul 2015 19:33:34 -0700
From: Arjan van de Ven <arjan@linux.intel.com>
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To: Andy Lutomirski <luto@kernel.org>, x86@kernel.org,
        linux-kernel@vger.kernel.org
CC: Oleg Nesterov <oleg@redhat.com>, Kees Cook <keescook@chromium.org>,
        Peter Zijlstra <peterz@infradead.org>, Borislav Petkov <bp@alien8.de>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] x86/kconfig/32: Mark CONFIG_VM86 as BROKEN
References: <23d4709cee2fe92c32d41b99c7a3c1823725925a.1436312944.git.luto@kernel.org>
In-Reply-To: <23d4709cee2fe92c32d41b99c7a3c1823725925a.1436312944.git.luto@kernel.org>
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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@linux.intel.com>


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