Re: [PATCH 2/2] powerpc/pkeys: key allocation/deallocation must not change pkey registers

[Thiago Jung Bauermann <bauerman@linux.ibm.com>]

Ram Pai <linuxram@us.ibm.com> writes:

> Key allocation and deallocation has the side effect of programming the
> UAMOR/AMR/IAMR registers. This is wrong, since its the responsibility of
> the application and not that of the kernel, to modify the permission on
> the key.
>
> Do not modify the pkey registers at key allocation/deallocation.
>
> This patch also fixes a bug where a sys_pkey_free() resets the UAMOR
> bits of the key, thus making its permissions unmodifiable from user
> space.  Latter if the same key gets reallocated from a different thread
> this thread will no longer be able to change the permissions on the key.
>
> Problem noticed/reported by Michael Ellermen while running
> selftests/core-pkeys
>
> Signed-off-by: Ram Pai <linuxram@us.ibm.com>
> ---
>  arch/powerpc/include/asm/pkeys.h |   11 -----------
>  arch/powerpc/mm/pkeys.c          |   27 ---------------------------
>  2 files changed, 0 insertions(+), 38 deletions(-)

LGTM.

Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>

-- 
Thiago Jung Bauermann
IBM Linux Technology Center