Re: [PATCH] Fix an overflow in range_to_mtrr func

[Yinghai Lu]

On Mon, May 28, 2012 at 5:29 AM, Zhenzhong Duan
<zhenzhong.duan@xxxxxxxxxx> wrote:
> When boot x86_64 kernel on sun G5+ with 4T mem, see an overflow in mtrr cleanup as below.
>
> *BAD*gran_size: 2G      chunk_size: 2G  num_reg: 10     lose cover RAM:
> -18014398505283592M
>
> This is because 1<<31 sign extended.
> Use explicit type conversion to force a 64bit constant to fix it.
> Useful for mem larger than or equal to 4T.
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/mtrr/cleanup.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mtrr/cleanup.c b/arch/x86/kernel/cpu/mtrr/cleanup.c
> index ac140c7..853a4c6 100644
> --- a/arch/x86/kernel/cpu/mtrr/cleanup.c
> +++ b/arch/x86/kernel/cpu/mtrr/cleanup.c
> @@ -266,7 +266,7 @@ range_to_mtrr(unsigned int reg, unsigned long range_startk,
>                if (align > max_align)
>                        align = max_align;
>
> -               sizek = 1 << align;
> +               sizek = (unsigned long)1 << align;

how about

            sizek = 1UL << align;


>                if (debug_print) {
>                        char start_factor = 'K', size_factor = 'K';
>                        unsigned long start_base, size_base;
> --
> 1.7.3
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/