Re: [PATCH] x86, powerpc : pkey-mprotect must allow pkey-0

[Ingo Molnar <mingo@kernel.org>]

* Ram Pai <linuxram@us.ibm.com> wrote:

> Once an address range is associated with an allocated pkey, it cannot be
> reverted back to key-0. There is no valid reason for the above behavior.  On
> the contrary applications need the ability to do so.
> 
> The patch relaxes the restriction.
> 
> Tested on powerpc and x86_64.
> 
> cc: Dave Hansen <dave.hansen@intel.com>
> cc: Michael Ellermen <mpe@ellerman.id.au>
> cc: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Ram Pai <linuxram@us.ibm.com>
> ---
>  arch/powerpc/include/asm/pkeys.h | 19 ++++++++++++++-----
>  arch/x86/include/asm/pkeys.h     |  5 +++--
>  2 files changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
> index 0409c80..3e8abe4 100644
> --- a/arch/powerpc/include/asm/pkeys.h
> +++ b/arch/powerpc/include/asm/pkeys.h
> @@ -101,10 +101,18 @@ static inline u16 pte_to_pkey_bits(u64 pteflags)
>  
>  static inline bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey)
>  {
> -	/* A reserved key is never considered as 'explicitly allocated' */
> -	return ((pkey < arch_max_pkey()) &&
> -		!__mm_pkey_is_reserved(pkey) &&
> -		__mm_pkey_is_allocated(mm, pkey));
> +	/* pkey 0 is allocated by default. */
> +	if (!pkey)
> +	       return true;
> +
> +	if (pkey < 0 || pkey >= arch_max_pkey())
> +	       return false;
> +
> +	/* reserved keys are never allocated. */
> +	if (__mm_pkey_is_reserved(pkey))
> +	       return false;

Please capitalize in comments consistently, i.e.:

	/* Reserved keys are never allocated: */

> +
> +	return(__mm_pkey_is_allocated(mm, pkey));

'return' is not a function.

Thanks,

	Ingo