Patch "KVM: ARM: vgic: plug irq injection race" has been added to the 3.14-stable tree

Patch "KVM: ARM: vgic: plug irq injection race" has been added to the 3.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    KVM: ARM: vgic: plug irq injection race

to the 3.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kvm-arm-vgic-plug-irq-injection-race.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 71afaba4a2e98bb7bdeba5078370ab43d46e67a1 Mon Sep 17 00:00:00 2001
From: Marc Zyngier <marc.zyngier@arm.com>
Date: Tue, 8 Jul 2014 12:09:00 +0100
Subject: KVM: ARM: vgic: plug irq injection race

From: Marc Zyngier <marc.zyngier@arm.com>

commit 71afaba4a2e98bb7bdeba5078370ab43d46e67a1 upstream.

[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.]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 virt/kvm/arm/vgic.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- 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;


Patches currently in stable-queue which might be from marc.zyngier@arm.com are

queue-3.14/arm-arm64-kvm-fix-use-of-wnr-bit-in-kvm_is_write_fault.patch
queue-3.14/kvm-arm-vgic-plug-irq-injection-race.patch