linux-kernel - Re: [PATCH v2] RO/NX protection for loadable kernel modules

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Message-ID: <817ecb6f0906300744i4f11d7faldd10ef3834582812@mail.gmail.com>
Date:	Tue, 30 Jun 2009 10:44:46 -0400
From:	Siarhei Liakh <sliakh.lkml@...il.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	James Morris <jmorris@...ei.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, Andi Kleen <ak@....de>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH v2] RO/NX protection for loadable kernel modules

On Tue, Jun 30, 2009 at 9:29 AM, Arjan van de Ven<arjan@...radead.org> wrote:
> On Tue, 30 Jun 2009 09:11:33 -0400
> Siarhei Liakh <sliakh.lkml@...il.com> wrote:
>
>> > (and one can still argue that making this an option is not even
>> > worth that, and just always do it unconditional)
>> >
>>
>> I can make NX unconditional. However, it will not reduce the number
>> of #ifdefs. There are two of them in the patch right now: one
>> controls the inclusion of two extra fields (init_ro_size,
>> core_ro_size) in struct module, and the other one controls the
>> inclusion of ALL patch code. The *_ro_size fields are used only for
>> RO, and are not used to set NX. Therefore, this #ifdef will stay even
>> if NX is unconditional. Since the second #ifdef controls ALL of the
>> patch's code it will also stay (to control RO part) when NX becomes
>> unconditional.
>>
>> Given that it will not reduce the number of #ifdefs, do you still
>> think that NX should be made unconditional?
>
> I think that not only NX should be made unconditional, I also think
> that the RO code should be unconditional.

So, the only conditional part would be the page-alignment of each of the
three parts of a module. Is that correct understanding?
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