Re: [PATCH] x86, mpx: Ensure unused arguments of prctl() MPX requests are 0

[Andi Kleen <andi@firstfloor.org>]

"Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> writes:

> From: Michael Kerrisk <mtk.manpages@gmail.com>
>
> commit fe8c7f5cbf91124987106faa3bdf0c8b955c4cf7 added two new prctl()
> operations, PR_MPX_ENABLE_MANAGEMENT and PR_MPX_DISABLE_MANAGEMENT.
> However, no checks were included to ensure that unused arguments
> are zero, as is done in many existing prctl()s and as should be 
> done for all new prctl()s. This patch adds the required checks.

This will break the existing gcc run time, which doesn't zero these
arguments.

-ANdi

>
> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
> ---
>  kernel/sys.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/kernel/sys.c b/kernel/sys.c
> index a8c9f5a..ea9c881 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -2210,9 +2210,13 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
>  		up_write(&me->mm->mmap_sem);
>  		break;
>  	case PR_MPX_ENABLE_MANAGEMENT:
> +		if (arg2 || arg3 || arg4 || arg5)
> +			return -EINVAL;
>  		error = MPX_ENABLE_MANAGEMENT(me);
>  		break;
>  	case PR_MPX_DISABLE_MANAGEMENT:
> +		if (arg2 || arg3 || arg4 || arg5)
> +			return -EINVAL;
>  		error = MPX_DISABLE_MANAGEMENT(me);
>  		break;
>  	default:
> -- 
> 1.9.3

-- 
ak@linux.intel.com -- Speaking for myself only

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