Ram Pai <linuxram@xxxxxxxxxx> writes:
> 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.
Please explain this in much more detail. Is it an ABI change?
And why did we just notice this?
> The patch relaxes the restriction.
>
> Tested on powerpc and x86_64.
Thanks, but please split the patch, one for each arch.
cheers
> 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;
> +
> + return(__mm_pkey_is_allocated(mm, pkey));
> }
>
> extern void __arch_activate_pkey(int pkey);
> @@ -150,7 +158,8 @@ static inline int mm_pkey_free(struct mm_struct *mm, int pkey)
> if (static_branch_likely(&pkey_disabled))
> return -1;
>
> - if (!mm_pkey_is_allocated(mm, pkey))
> + /* pkey 0 cannot be freed */
> + if (!pkey || !mm_pkey_is_allocated(mm, pkey))
> return -EINVAL;
>
> /*
> diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h
> index a0ba1ff..6ea7486 100644
> --- a/arch/x86/include/asm/pkeys.h
> +++ b/arch/x86/include/asm/pkeys.h
> @@ -52,7 +52,7 @@ bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey)
> * from pkey_alloc(). pkey 0 is special, and never
> * returned from pkey_alloc().
> */
> - if (pkey <= 0)
> + if (pkey < 0)
> return false;
> if (pkey >= arch_max_pkey())
> return false;
> @@ -92,7 +92,8 @@ int mm_pkey_alloc(struct mm_struct *mm)
> static inline
> int mm_pkey_free(struct mm_struct *mm, int pkey)
> {
> - if (!mm_pkey_is_allocated(mm, pkey))
> + /* pkey 0 is special and can never be freed */
> + if (!pkey || !mm_pkey_is_allocated(mm, pkey))
> return -EINVAL;
>
> mm_set_pkey_free(mm, pkey);
> --
> 1.8.3.1
