KVM: s390: sthyi: fix specification exception detection

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")
Cc: <stable@vger.kernel.org> # 4.8+
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>

diff --git a/arch/s390/kvm/sthyi.c b/arch/s390/kvm/sthyi.c
index 2773a2f6a5c45cbe8491e9d2bd99496a0b7b9609..a2e5c24f47a7471a1e7730f654b8ce4599434ef0 100644 (file)
--- 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.