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SubjectRe: [PATCH] fix mmap random address range on x86 (try2)
On Mon, 28 Feb 2011 15:53:03 +0100 Ludwig Nussel wrote:

> On x86 casting the unsigned int result of get_random_int() to long
> may result in a negative value. On x86 the range of mmap_rnd()
> therefore was -255 to 255. The 32bit mode on x86_64 used 0 to 255 as
> intended.
>
> The bug was introduced by commit 675a081 in January 2008.
>
> Signed-off-by: Ludwig Nussel <ludwig.nussel@suse.de>
> ---
> arch/x86/mm/mmap.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
> index 1dab519..f927429 100644
> --- a/arch/x86/mm/mmap.c
> +++ b/arch/x86/mm/mmap.c
> @@ -87,9 +87,9 @@ static unsigned long mmap_rnd(void)
> */
> if (current->flags & PF_RANDOMIZE) {
> if (mmap_is_ia32())
> - rnd = (long)get_random_int() % (1<<8);
> + rnd = get_random_int() % (1<<8);
> else
> - rnd = (long)(get_random_int() % (1<<28));
> + rnd = get_random_int() % (1<<28);
> }
> return rnd << PAGE_SHIFT;
> }
> --

Is there a test case for this?
Can it be tested/checked/observed?

thanks,
---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***


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