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

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Message-ID: <4E237893.70801@zytor.com>
Date:	Sun, 17 Jul 2011 17:04:35 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Eric Paris <eparis@...isplace.org>
CC:	Mike Waychison <mikew@...gle.com>,
	"Andrew G. Morgan" <agm@...gle.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Klibc mailing list <klibc@...or.com>
Subject: Re: [PATCH 2/2] x86: Allow disabling of sys_iopl, sys_ioperm

On 07/17/2011 04:19 PM, Eric Paris wrote:
> On Sat, Jul 16, 2011 at 12:42 AM, Mike Waychison <mikew@...gle.com> wrote:
>> On Fri, Jul 15, 2011 at 3:30 PM, Andrew G. Morgan <agm@...gle.com> wrote:
>>> I'd put it in kinit too.
>>>
>>> I think you may have to think about the call_usermodehelper code, and
>>> you might want to look at dropping CAP_SYS_MODULE too.
>>
>> Looks like usermodehelpers are configurable for both the inheritable
>> set and the bounding set via /proc/sys/kernel/usermodehelper/bset and
>> /proc/sys/kernel/usermodehelper/inheritable thanks to Eric Paris
>> (17f60a7da, available in 3.0-rc1).
> 
> If you look in Fedora and RHEL you'll see that we actually already
> provide a dracut module (dracut-caps) which can be used to create an
> initrd which contains all of the modules you need to load, it loads
> them, and then will drop all of the caps that you want to drop.   Good
> to see we already solved this problem once!!  (although it requires
> that your kernel and initrd not be in a place that your root user can
> modify it, easy to do in the virt space, no so easy in the real
> hardware world)
> 

Have you considered separating out the kernel-specific portions into a
separate initramfs file (preferrably one which could be built from a
kernel build tree).  The whole dependency of kernels with initramfs is a
huge pain for kernel development and debugging...

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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