[PATCH 3.19 146/175] KVM: s390: floating irqs: fix user triggerable endless loop

Greg Kroah-Hartman
2015-03-04T06:33:06Z

From: David Hildenbrand <dahi@linux.vnet.ibm.com>

commit 8e2207cdd087ebb031e9118d1fd0902c6533a5e5 upstream.

If a vm with no VCPUs is created, the injection of a floating irq
leads to an endless loop in the kernel.

Let's skip the search for a destination VCPU for a floating irq if no
VCPUs were created.

Reviewed-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/s390/kvm/interrupt.c | 2 ++
1 file changed, 2 insertions(+)

--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -1197,6 +1197,8 @@ static int __inject_vm(struct kvm *kvm,
list_add_tail(&inti->list, &iter->list);
}
atomic_set(&fi->active, 1);
+ if (atomic_read(&kvm->online_vcpus) == 0)
+ goto unlock_fi;
sigcpu = find_first_bit(fi->idle_mask, KVM_MAX_VCPUS);
if (sigcpu == KVM_MAX_VCPUS) {
do {