linux-kernel - Re: [RFC v5 13/38] x86: disallow pkey creation with PKEY_DISABLE

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Date:   Tue, 11 Jul 2017 11:12:37 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Ram Pai <linuxram@...ibm.com>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, x86@...nel.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Cc:     benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
        bsingharora@...il.com, hbabu@...ibm.com, arnd@...db.de,
        akpm@...ux-foundation.org, corbet@....net, mingo@...hat.com
Subject: Re: [RFC v5 13/38] x86: disallow pkey creation with
 PKEY_DISABLE_EXECUTE

On 07/05/2017 02:21 PM, Ram Pai wrote:
> x86 does not support disabling execute permissions on a pkey.
> 
> Signed-off-by: Ram Pai <linuxram@...ibm.com>
> ---
>  arch/x86/kernel/fpu/xstate.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
> index c24ac1e..d582631 100644
> --- a/arch/x86/kernel/fpu/xstate.c
> +++ b/arch/x86/kernel/fpu/xstate.c
> @@ -900,6 +900,9 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
>  	if (!boot_cpu_has(X86_FEATURE_OSPKE))
>  		return -EINVAL;
>  
> +	if (init_val & PKEY_DISABLE_EXECUTE)
> +		return -EINVAL;

I'd really rather that we define a supported mask instead of having each
architecture go through and list which ones it supports.