Re: [PATCH] powerpc/pkeys: copy pkey-tracking-information at fork()

[Michael Ellerman]

Hi Ram,

Thanks for fixing this.

Ram Pai <linux...@us.ibm.com> writes:
> diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
> index b271b28..5d65c47 100644
> --- a/arch/powerpc/mm/pkeys.c
> +++ b/arch/powerpc/mm/pkeys.c
> @@ -414,3 +414,10 @@ bool arch_vma_access_permitted(struct vm_area_struct 
> *vma, bool write,
>  
>       return pkey_access_permitted(vma_pkey(vma), write, execute);
>  }
> +
> +void arch_dup_pkeys(struct mm_struct *oldmm, struct mm_struct *mm)
> +{
> +     /* Duplicate the oldmm pkey state in mm: */
> +     mm_pkey_allocation_map(mm) = mm_pkey_allocation_map(oldmm);
> +     mm->context.execute_only_pkey = oldmm->context.execute_only_pkey;
> +}

Shouldn't this check if pkeys are actually in use?

eg:

diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index cf87dddefbdc..587807763737 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -418,6 +418,9 @@ bool arch_vma_access_permitted(struct vm_area_struct *vma, 
bool write,
 
 void arch_dup_pkeys(struct mm_struct *oldmm, struct mm_struct *mm)
 {
+       if (static_branch_likely(&pkey_disabled))
+               return;
+
        /* Duplicate the oldmm pkey state in mm: */
        mm_pkey_allocation_map(mm) = mm_pkey_allocation_map(oldmm);
        mm->context.execute_only_pkey = oldmm->context.execute_only_pkey;


Ideally we'd actually do it in the inline so that the function call to
arch_dup_pkeys() can be avoided. But it looks like header dependencies
might make that hard.

cheers