linux-kernel - Re: [PATCH V9] RO/NX protection for loadable kernel modules

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Message-Id: <201002020819.55499.rusty@rustcorp.com.au>
Date:	Tue, 2 Feb 2010 08:19:55 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Siarhei Liakh <sliakh.lkml@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-next@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.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>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Dave Jones <davej@...hat.com>
Subject: Re: [PATCH V9] RO/NX protection for loadable kernel modules

On Tue, 2 Feb 2010 02:59:41 am Siarhei Liakh wrote:
> V9: coding style fixes

But not compile tested:

> +void set_page_attributes(void *start, void *end,
> +		void (*set)(unsigned long start, int num_pages))
> +{
> +	unsigned long begin_pfn = PFN_DOWN((unsigned long)start);
> +	unsigned long end_pfn = PFN_DOWN((unsigned long)end);
> +	if (end_pfn > begin_pfn)
> +		set(begin_pfn << PAGE_SHIFT, end_pfn - begin_pfn);
> +}
...
> +	if (ro_size > 0) {
> +		set_page_attributes((unsigned long)base,
> +					(unsigned long)base + ro_size,
> +					set_memory_ro);

The casts here should cause a warning. 

> +	if (total_size > text_size) {
> +		begin_pfn = PFN_UP((unsigned long)base + text_size);
> +		end_pfn = PFN_UP((unsigned long)base + total_size);
> +		if (end_pfn > begin_pfn)
> +			set_memory_nx(begin_pfn << PAGE_SHIFT,
> +						end_pfn - begin_pfn);

Use the helper here too?

> +		if ((mod->module_core) && (mod->core_text_size)) {
> +			set_page_attributes((unsigned long)mod->module_core,
> +						(unsigned long)mod->module_core
> +							+ mod->core_text_size,
> +						set_memory_rw);
> +		}
> +		if ((mod->module_init) && (mod->init_text_size)) {
> +			set_page_attributes((unsigned long)mod->module_init,
> +						(unsigned long)mod->module_init
> +							+ mod->init_text_size,
> +						set_memory_rw);

More unwanted casts...

> +			set_page_attributes((unsigned long)mod->module_core,
> +						(unsigned long)mod->module_core
> +							+ mod->core_text_size,
> +						set_memory_ro);
> +		}
> +		if ((mod->module_init) && (mod->init_text_size)) {
> +			set_page_attributes((unsigned long)mod->module_init,
> +						(unsigned long)mod->module_init
> +							+ mod->init_text_size,
> +						set_memory_ro);

Here, too.

Thanks,
Rusty.
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