linux-kernel - Re: [PATCH 2/2] x86: Allow disabling of sys_iopl, sys

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Message-ID: <CAGTjWtA5qobWAZb=SbM1y5SFtDKPuJVuAsbDKmkaxxL7mA6OKg@mail.gmail.com>
Date:	Thu, 14 Jul 2011 16:20:59 -0700
From:	Mike Waychison <mikew@...gle.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86: Allow disabling of sys_iopl, sys_ioperm

On Thu, Jul 14, 2011 at 4:00 PM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
>> > a) you can do this with a security module
>>
>> I can?   How?   The whole LSM approach seems intractable to me.
>
> It would certainly need some trivial tweaking (to be specific we'd need
> to move from capable(x) to capable_syscall(x, syscall_code) for those
> interfaces that mattered, but that would probably be a good thing anyway
> from the point of view of beating the capability model into something more
> flexible and would help stuff like SELinux as well I think.

The idea of building more obtuse logic on top of posix capabilities
made me puke in my mouth :(

>
> We have an underlying separation of security from the other details - we
> really should keep it clean that way.

An aspect oriented approach to security is probably fine for
environments where you want to allow somebody access to features.

In my case, I simply don't want these "features", which is why I took
the compile time approach to turning this stuff off.  I realize that
these syscalls (and the /dev/port interface) are not comprehensive (I
didn't say they were either).  I'm happy though to take suggestions
for stuff I probably should be disabling considering my goal of making
it difficult for root to compromise a system.  And yes, modules are
disabled :)
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