From: Claudio Imbrenda imbrenda@linux.ibm.com
[ Upstream commit d4074324b07a94a1fca476d452dfbb3a4e7bf656 ]
If kvm_s390_pv_destroy_cpu is called more than once, we risk calling free_page on a random page, since the sidad field is aliased with the gbea, which is not guaranteed to be zero.
This can happen, for example, if userspace calls the KVM_PV_DISABLE IOCTL, and it fails, and then userspace calls the same IOCTL again. This scenario is only possible if KVM has some serious bug or if the hardware is broken.
The solution is to simply return successfully immediately if the vCPU was already non secure.
Signed-off-by: Claudio Imbrenda imbrenda@linux.ibm.com Fixes: 19e1227768863a1469797c13ef8fea1af7beac2c ("KVM: S390: protvirt: Introduce instruction data area bounce buffer") Reviewed-by: Janosch Frank frankja@linux.ibm.com Reviewed-by: Christian Borntraeger borntraeger@de.ibm.com Message-Id: 20210920132502.36111-3-imbrenda@linux.ibm.com Signed-off-by: Janosch Frank frankja@linux.ibm.com Signed-off-by: Christian Borntraeger borntraeger@de.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/kvm/pv.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c index c8841f476e913..0a854115100b4 100644 --- a/arch/s390/kvm/pv.c +++ b/arch/s390/kvm/pv.c @@ -16,18 +16,17 @@
int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc) { - int cc = 0; + int cc;
- if (kvm_s390_pv_cpu_get_handle(vcpu)) { - cc = uv_cmd_nodata(kvm_s390_pv_cpu_get_handle(vcpu), - UVC_CMD_DESTROY_SEC_CPU, rc, rrc); + if (!kvm_s390_pv_cpu_get_handle(vcpu)) + return 0; + + cc = uv_cmd_nodata(kvm_s390_pv_cpu_get_handle(vcpu), UVC_CMD_DESTROY_SEC_CPU, rc, rrc); + + KVM_UV_EVENT(vcpu->kvm, 3, "PROTVIRT DESTROY VCPU %d: rc %x rrc %x", + vcpu->vcpu_id, *rc, *rrc); + WARN_ONCE(cc, "protvirt destroy cpu failed rc %x rrc %x", *rc, *rrc);
- KVM_UV_EVENT(vcpu->kvm, 3, - "PROTVIRT DESTROY VCPU %d: rc %x rrc %x", - vcpu->vcpu_id, *rc, *rrc); - WARN_ONCE(cc, "protvirt destroy cpu failed rc %x rrc %x", - *rc, *rrc); - } /* Intended memory leak for something that should never happen. */ if (!cc) free_pages(vcpu->arch.pv.stor_base,