[for,3.14.y,stable,02/22] KVM: ARM: vgic: plug irq injection race

Message ID 1435661350-8060-3-git-send-email-shannon.zhao@linaro.org
State New
Headers show

Commit Message

Shannon Zhao June 30, 2015, 10:48 a.m.
From: Marc Zyngier <marc.zyngier@arm.com>

Since we don't backport commit 227844f (arm/arm64: KVM: Rename irq_state
to irq_pending) for linux-3.14.y, here we still use vgic_update_irq_state
instead of vgic_update_irq_pending.

commit 71afaba4a2e98bb7bdeba5078370ab43d46e67a1 upstream.

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>
Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
---
 virt/kvm/arm/vgic.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Patch

diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 1316e55..2187318 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -1387,7 +1387,8 @@  out:
 int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int irq_num,
 			bool level)
 {
-	if (vgic_update_irq_state(kvm, cpuid, irq_num, level))
+	if (likely(vgic_initialized(kvm)) &&
+	    vgic_update_irq_state(kvm, cpuid, irq_num, level))
 		vgic_kick_vcpus(kvm);
 
 	return 0;