When running a guest on a POWER9 system with the in-kernel XICS
emulation disabled (for example by running QEMU with the parameter
"-machine pseries,kernel_irqchip=off"), the kernel does not pass
the XICS-related hypercalls such as H_CPPR up to userspace for
emulation there as it should.
The reason for this is that the real-mode handlers for these
hypercalls don't check whether a XICS device has been instantiated
before calling the xics-on-xive code. That code doesn't check
either, leading to potential NULL pointer dereferences because
vcpu->arch.xive_vcpu is NULL. Those dereferences won't cause an
exception in real mode but will lead to kernel memory corruption.
This fixes it by adding kvmppc_xics_enabled() checks before calling
the XICS functions.
Cc: stable@xxxxxxxxxxxxxxx # v4.11+
Fixes: 5af50993850a ("KVM: PPC: Book3S HV: Native usage of the XIVE interrupt controller")
Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
---
arch/powerpc/kvm/book3s_hv_builtin.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c
index 2791922e97e2..e38cc2df6d2a 100644
--- a/arch/powerpc/kvm/book3s_hv_builtin.c
+++ b/arch/powerpc/kvm/book3s_hv_builtin.c
@@ -529,6 +529,8 @@ static inline bool is_rm(void)
unsigned long kvmppc_rm_h_xirr(struct kvm_vcpu *vcpu)
{
+ if (!kvmppc_xics_enabled(vcpu))
+ return H_TOO_HARD;
if (xive_enabled()) {
if (is_rm())
return xive_rm_h_xirr(vcpu);
@@ -541,6 +543,8 @@ unsigned long kvmppc_rm_h_xirr(struct kvm_vcpu *vcpu)
unsigned long kvmppc_rm_h_xirr_x(struct kvm_vcpu *vcpu)
{
+ if (!kvmppc_xics_enabled(vcpu))
+ return H_TOO_HARD;
vcpu->arch.gpr[5] = get_tb();
if (xive_enabled()) {
if (is_rm())
@@ -554,6 +558,8 @@ unsigned long kvmppc_rm_h_xirr_x(struct kvm_vcpu *vcpu)
unsigned long kvmppc_rm_h_ipoll(struct kvm_vcpu *vcpu, unsigned long server)
{
+ if (!kvmppc_xics_enabled(vcpu))
+ return H_TOO_HARD;
if (xive_enabled()) {
if (is_rm())
return xive_rm_h_ipoll(vcpu, server);
@@ -567,6 +573,8 @@ unsigned long kvmppc_rm_h_ipoll(struct kvm_vcpu *vcpu, unsigned long server)
int kvmppc_rm_h_ipi(struct kvm_vcpu *vcpu, unsigned long server,
unsigned long mfrr)
{
+ if (!kvmppc_xics_enabled(vcpu))
+ return H_TOO_HARD;
if (xive_enabled()) {
if (is_rm())
return xive_rm_h_ipi(vcpu, server, mfrr);
@@ -579,6 +587,8 @@ int kvmppc_rm_h_ipi(struct kvm_vcpu *vcpu, unsigned long server,
int kvmppc_rm_h_cppr(struct kvm_vcpu *vcpu, unsigned long cppr)
{
+ if (!kvmppc_xics_enabled(vcpu))
+ return H_TOO_HARD;
if (xive_enabled()) {
if (is_rm())
return xive_rm_h_cppr(vcpu, cppr);
@@ -591,6 +601,8 @@ int kvmppc_rm_h_cppr(struct kvm_vcpu *vcpu, unsigned long cppr)
int kvmppc_rm_h_eoi(struct kvm_vcpu *vcpu, unsigned long xirr)
{
+ if (!kvmppc_xics_enabled(vcpu))
+ return H_TOO_HARD;
if (xive_enabled()) {
if (is_rm())
return xive_rm_h_eoi(vcpu, xirr);
--
2.11.0
