linux-kernel - Re: [PATCH v4] RO/NX protection for loadable kernel modules

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Date:	Wed, 8 Jul 2009 18:31:59 -0400
From:	Siarhei Liakh <sliakh.lkml@...il.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	James Morris <jmorris@...ei.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@....de>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [PATCH v4] RO/NX protection for loadable kernel modules

> I like it, you can already put
>
> Acked-by: Arjan van de Ven <arjan@...ux.intel.com>

Thanks, I will add this to V5.

...
>> +             /*Set text RO if there are still pages between begin
>> and end*/
>> +             if (end_addr > begin_addr) {
>> +                     pg_count = PFN_DOWN(end_addr - 1) -
>> +                                     PFN_DOWN(begin_addr) + 1;
>> +                     DEBUGP("  RO: 0x%lx %lu\n", begin_addr,
>> pg_count);
>> +                     set_memory_ro(begin_addr, pg_count);
>> +             } else {
...
> I *think* this can be done as
>
> begin_pfn = PFN_UP( (base);
> end_pfn = PFN_DOWN(base + ro_size);
>
> if (end_pfn > begin_pfn)
>        set_memory_ro(begin_pfn >> PAGE_SHIFT, end_pfn - begin_pfn);
>
> (note that I think the +1 you have might be buggy)

The +1 is necessary because of (end_addr - 1). However, I like your
way better, so I will incorporate it in V5.
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