Re: [PATCH 4/4] KVM: s390: Fix skey emulation permission check

[Cornelia Huck <cohuck@redhat.com>]

On Tue,  5 Dec 2017 09:33:21 +0100
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> From: Janosch Frank <frankja@linux.vnet.ibm.com>
> 
> All skey functions call skey_check_enable at their start, which checks
> if we are in the PSTATE and injects a privileged operation exception
> if we are.
> 
> Unfortunately they continue processing afterwards and perform the
> operation anyhow as skey_check_enable does not deliver an error if the
> exception injection was successful.
> 
> Let's move the PSTATE check into the skey functions and exit them on
> such an occasion, also we now do not enable skey handling anymore in
> such a case.
> 
> Signed-off-by: Janosch Frank <frankja@linux.vnet.ibm.com>
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Fixes: a7e19ab ("KVM: s390: handle missing storage-key facility")
> Cc: <stable@vger.kernel.org> # v4.8+
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  arch/s390/kvm/priv.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

This reminds me of something I stumbled upon the other day:

handle_ri() and handle_gs() (both implemented in priv.c) don't seem to
have a check for PSTATE, yet they enable ri/gs before retrying the
instruction. Is that correct?