KVM: add KVM_USERSPACE_IRQ_SOURCE_ID assertions

Make sure kvm_request_irq_source_id() never returns
KVM_USERSPACE_IRQ_SOURCE_ID.

Likewise, check that kvm_free_irq_source_id() never accepts
KVM_USERSPACE_IRQ_SOURCE_ID.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index db75045f22f6..aa5d1e5c497e 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -72,11 +72,15 @@ int kvm_request_irq_source_id(struct kvm *kvm)
         unsigned long *bitmap = &kvm->arch.irq_sources_bitmap;
         int irq_source_id = find_first_zero_bit(bitmap,
                                 sizeof(kvm->arch.irq_sources_bitmap));
+
         if (irq_source_id >= sizeof(kvm->arch.irq_sources_bitmap)) {
                 printk(KERN_WARNING "kvm: exhaust allocatable IRQ sources!\n");
-                irq_source_id = -EFAULT;
-        } else
-                set_bit(irq_source_id, bitmap);
+                return -EFAULT;
+        }
+
+        ASSERT(irq_source_id != KVM_USERSPACE_IRQ_SOURCE_ID);
+        set_bit(irq_source_id, bitmap);
+
         return irq_source_id;
 }
 
@@ -84,7 +88,9 @@ void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id)
 {
         int i;
 
-        if (irq_source_id <= 0 ||
+        ASSERT(irq_source_id != KVM_USERSPACE_IRQ_SOURCE_ID);
+
+        if (irq_source_id < 0 ||
             irq_source_id >= sizeof(kvm->arch.irq_sources_bitmap)) {
                 printk(KERN_ERR "kvm: IRQ source ID out of range!\n");
                 return;