linux-kernel - Re: [PATCH] avr32: fix integer overflow in ELF_ET_DYN

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Message-ID: <20150325062933.GC3771@samfundet.no>
Date:	Wed, 25 Mar 2015 07:29:33 +0100
From:	Hans-Christian Egtvedt <egtvedt@...fundet.no>
To:	Andrey Ryabinin <a.ryabinin@...sung.com>
Cc:	Haavard Skinnemoen <hskinnemoen@...il.com>,
	linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
	Yury Gribov <y.gribov@...sung.com>
Subject: Re: [PATCH] avr32: fix integer overflow in ELF_ET_DYN_BASE

Around Tue 24 Mar 2015 18:31:22 +0300 or thereabout, Andrey Ryabinin wrote:
> Almost all arches define ELF_ET_DYN_BASE as 2/3 of TASK_SIZE.
> Though it seems that some architectures do this in a wrong way.
> The problem is that 2*TASK_SIZE may overflow 32-bits so
> the real ELF_ET_DYN_BASE becomes wrong.
> Fix this overflow by dividing TASK_SIZE prior to multiplying:
> 	 (TASK_SIZE / 3 * 2)

Thank you for fixing (-:

> Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
>

Acked-by: Hans-Christian Egtvedt <egtvedt@...fundet.no>

Added to for-linus branch in
git://git.kernel.org/pub/scm/linux/kernel/git/egtvedt/linux-avr32.git
queued for Linux 4.1.

> ---
>  arch/avr32/include/asm/elf.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/avr32/include/asm/elf.h b/arch/avr32/include/asm/elf.h
> index d232888..0388ece 100644
> --- a/arch/avr32/include/asm/elf.h
> +++ b/arch/avr32/include/asm/elf.h
> @@ -84,7 +84,7 @@ typedef struct user_fpu_struct elf_fpregset_t;
>     the loader.  We need to make sure that it is out of the way of the program
>     that it will "exec", and that there is sufficient room for the brk.  */
>  
> -#define ELF_ET_DYN_BASE         (2 * TASK_SIZE / 3)
> +#define ELF_ET_DYN_BASE         (TASK_SIZE / 3 * 2)
>  
>  
>  /* This yields a mask that user programs can use to figure out what
-- 
Best regards,
Hans-Christian Egtvedt
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