If the KVM_S390_MEM_OP ioctl is called with an access register >= 16, then there is certainly a bug in the calling userspace application. We check for wrong access registers, but only if the vCPU was already in the access register mode before (i.e. the SIE block has recorded it). The check is also buried somewhere deep in the calling chain (in the function ar_translation()), so this is somewhat hard to find. It's better to always report an error to the userspace in case this field is set wrong, and it's safer in the KVM code if we block wrong values here early instead of relying on a check somewhere deep down the calling chain, so let's add another check to kvm_s390_guest_mem_op() directly. Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx> --- arch/s390/kvm/kvm-s390.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index f329dcb3f44c..725690853cbd 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -4255,7 +4255,7 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu, const u64 supported_flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION | KVM_S390_MEMOP_F_CHECK_ONLY; - if (mop->flags & ~supported_flags) + if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS) return -EINVAL; if (mop->size > MEM_OP_MAX_SIZE) -- 2.18.1
