KVM: s390: fix possible null pointer dereference in pending_irqs()

Assure a GISA is in use before accessing the IPM to avoid a
null pointer dereference issue.

Signed-off-by: Michael Mueller <mimu@linux.ibm.com>
Reported-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20190131085247.13826-16-mimu@linux.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index dc446203e5a4fba85e4607fef3061eb467b74c77..82162867f378d225ede29ff32adee1983072a7ac 100644 (file)
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -329,9 +329,13 @@ static inline unsigned long pending_irqs_no_gisa(struct kvm_vcpu *vcpu)
 
 static inline unsigned long pending_irqs(struct kvm_vcpu *vcpu)
 {
-       return pending_irqs_no_gisa(vcpu) |
-               gisa_get_ipm(vcpu->kvm->arch.gisa_int.origin) <<
-                       IRQ_PEND_IO_ISC_7;
+       struct kvm_s390_gisa_interrupt *gi = &vcpu->kvm->arch.gisa_int;
+       unsigned long pending_mask;
+
+       pending_mask = pending_irqs_no_gisa(vcpu);
+       if (gi->origin)
+               pending_mask |= gisa_get_ipm(gi->origin) << IRQ_PEND_IO_ISC_7;
+       return pending_mask;
 }
 
 static inline int isc_to_irq_type(unsigned long isc)