KVM: ARM: vgic: plug irq injection race

As it stands, nothing prevents userspace from injecting an interrupt
before the guest's GIC is actually initialized.

This goes unnoticed so far (as everything is pretty much statically
allocated), but ends up exploding in a spectacular way once we switch
to a more dynamic allocation (the GIC data structure isn't there yet).

The fix is to test for the "ready" flag in the VGIC distributor before
trying to inject the interrupt. Note that in order to avoid breaking
userspace, we have to ignore what is essentially an error.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
(cherry picked from commit 71afaba4a2e98bb7bdeba5078370ab43d46e67a1)
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index ff88dbcacc292dfcf8d45ecae297b3efbb7b6057..5744a49d76805ccbc5c36c37a106f1ba8d1a597a 100644 (file)
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -1585,7 +1585,8 @@ out:
 int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int irq_num,
                        bool level)
 {
-       if (vgic_update_irq_pending(kvm, cpuid, irq_num, level))
+       if (likely(vgic_initialized(kvm)) &&
+           vgic_update_irq_pending(kvm, cpuid, irq_num, level))
                vgic_kick_vcpus(kvm);
 
        return 0;