[PATCH 4.12 33/99] KVM: s390: sthyi: fix specification exception detection

Greg Kroah-Hartman
2017-08-28T09:13:44Z

From: Heiko Carstens <heiko.carstens@de.ibm.com>

commit 857b8de96795646c5891cf44ae6fb19b9ff74bf9 upstream.

sthyi should only generate a specification exception if the function
code is zero and the response buffer is not on a 4k boundary.

The current code would also test for unknown function codes if the
response buffer, that is currently only defined for function code 0,
is not on a 4k boundary and incorrectly inject a specification
exception instead of returning with condition code 3 and return code 4
(unsupported function code).

Fix this by moving the boundary check.

Fixes: 95ca2cb57985 ("KVM: s390: Add sthyi emulation")
Reviewed-by: Janosch Frank <frankja@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/s390/kvm/sthyi.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/arch/s390/kvm/sthyi.c
+++ b/arch/s390/kvm/sthyi.c
@@ -425,7 +425,7 @@ int handle_sthyi(struct kvm_vcpu *vcpu)
VCPU_EVENT(vcpu, 3, "STHYI: fc: %llu addr: 0x%016llx", code, addr);
trace_kvm_s390_handle_sthyi(vcpu, code, addr);

- if (reg1 == reg2 || reg1 & 1 || reg2 & 1 || addr & ~PAGE_MASK)
+ if (reg1 == reg2 || reg1 & 1 || reg2 & 1)
return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);

if (code & 0xffff) {
@@ -433,6 +433,9 @@ int handle_sthyi(struct kvm_vcpu *vcpu)
goto out;
}

+ if (addr & ~PAGE_MASK)
+ return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
+
/*
* If the page has not yet been faulted in, we want to do that
* now and not after all the expensive calculations.