[PATCH v3 3/4] KVM: PPC: Book3S HV: XICS: Avoid NULL ptr deref in kvmppc_xive_cleanup_vcpu()

[Gautam Menghani <gautam@linux.ibm.com>]

In kvmppc_xive_connect_vcpu() if there is a failure before
xc->vp_ipi_data is setup, it can result in a NULL pointer dereference in
kvmppc_xive_cleanup_vcpu() when accessing the MMIO page in
xive_vm_esb_load(). Fix this by adding a check before masking
the VP IPI before accessing the MMIO pages.

Fixes: 5af50993850a ("KVM: PPC: Book3S HV: Native usage of the XIVE interrupt controller")
Cc: stable@vger.kernel.org # 4.12+
Signed-off-by: Gautam Menghani <gautam@linux.ibm.com>
---
v3:
1. Add some more info to the patch description.

v2:
1. New patch - Introduced to fix the scenario where NULL ptr deref is
possible. (Sashiko)

 arch/powerpc/kvm/book3s_xive.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c
index 67219044fb8c..b27127c43315 100644
--- a/arch/powerpc/kvm/book3s_xive.c
+++ b/arch/powerpc/kvm/book3s_xive.c
@@ -1818,7 +1818,8 @@ void kvmppc_xive_cleanup_vcpu(struct kvm_vcpu *vcpu)
 	kvmppc_xive_disable_vcpu_interrupts(vcpu);
 
 	/* Mask the VP IPI */
-	xive_vm_esb_load(&xc->vp_ipi_data, XIVE_ESB_SET_PQ_01);
+	if (xc->vp_ipi_data.eoi_mmio)
+		xive_vm_esb_load(&xc->vp_ipi_data, XIVE_ESB_SET_PQ_01);
 
 	/* Free escalations */
 	for (i = 0; i < KVMPPC_XIVE_Q_COUNT; i++) {
-- 
2.54.0