linux-kernel - Re: [PATCH v2] tile: support ASLR fully

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Date:	Mon, 19 Aug 2013 14:01:51 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Tony Lu <zlu@...era.com>
Cc:	linux-kernel@...r.kernel.org, cmetcalf@...era.com
Subject: Re: [PATCH v2] tile: support ASLR fully

On Tue, 13 Aug 2013, Tony Lu wrote:

> With this change, tile Linux now supports address-space layout
> randomization for shared objects, stack, heap and vdso.
> 
> Signed-off-by: Tony Lu <zlu@...era.com>
> Signed-off-by: Chris Metcalf <cmetcalf@...era.com>
> ---
> v2: implement Jiri Kosina's suggestion to copy the math in
> mmap_rnd() for x86.

Feel free to add:

	Acked-by: Jiri Kosina <jkosina@...e.cz>

Thanks.

>  arch/tile/include/asm/elf.h |  4 ++++
>  arch/tile/mm/mmap.c         | 24 ++++++++++++++++++++++--
>  2 files changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/tile/include/asm/elf.h b/arch/tile/include/asm/elf.h
> index 31d854f..e1da88e 100644
> --- a/arch/tile/include/asm/elf.h
> +++ b/arch/tile/include/asm/elf.h
> @@ -137,6 +137,10 @@ do { \
>  	NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_BASE); \
>  } while (0)
>  
> +struct mm_struct;
> +extern unsigned long arch_randomize_brk(struct mm_struct *mm);
> +#define arch_randomize_brk arch_randomize_brk
> +
>  #ifdef CONFIG_COMPAT
>  
>  #define COMPAT_ELF_PLATFORM "tilegx-m32"
> diff --git a/arch/tile/mm/mmap.c b/arch/tile/mm/mmap.c
> index d67d91e..4b99344 100644
> --- a/arch/tile/mm/mmap.c
> +++ b/arch/tile/mm/mmap.c
> @@ -58,16 +58,36 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
>  #else
>  	int is_32bit = 0;
>  #endif
> +	unsigned long random_factor = 0UL;
> +
> +	/*
> +	 *  8 bits of randomness in 32bit mmaps, 24 address space bits
> +	 * 12 bits of randomness in 64bit mmaps, 28 address space bits
> +	 */
> +	if (current->flags & PF_RANDOMIZE) {
> +		if (is_32bit)
> +			random_factor = get_random_int() % (1<<8);
> +		else
> +			random_factor = get_random_int() % (1<<12);
> +		
> +		random_factor <<= PAGE_SHIFT;
> +	}
>  
>  	/*
>  	 * Use standard layout if the expected stack growth is unlimited
>  	 * or we are running native 64 bits.
>  	 */
> -	if (!is_32bit || rlimit(RLIMIT_STACK) == RLIM_INFINITY) {
> -		mm->mmap_base = TASK_UNMAPPED_BASE;
> +	if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) {
> +		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
>  		mm->get_unmapped_area = arch_get_unmapped_area;
>  	} else {
>  		mm->mmap_base = mmap_base(mm);
>  		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
>  	}
>  }
> +
> +unsigned long arch_randomize_brk(struct mm_struct *mm)
> +{
> +	unsigned long range_end = mm->brk + 0x02000000;
> +	return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
> +}
> -- 
> 1.8.3.1
> 

-- 
Jiri Kosina
SUSE Labs
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