[3.16.y-ckt stable] Patch "KVM: s390: floating irqs: fix user triggerable endless loop" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    KVM: s390: floating irqs: fix user triggerable endless loop

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt8.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From f823f3b36e1c9d39a202ae6f7785f22498858ee1 Mon Sep 17 00:00:00 2001
From: David Hildenbrand <dahi at linux.vnet.ibm.com>
Date: Thu, 15 Jan 2015 17:56:18 +0100
Subject: KVM: s390: floating irqs: fix user triggerable endless loop

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 at linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck at de.ibm.com>
Signed-off-by: David Hildenbrand <dahi at linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger at de.ibm.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/s390/kvm/interrupt.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index e2354f97264e..f19702fc89ec 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -925,6 +925,8 @@ static int __inject_vm(struct kvm *kvm, struct kvm_s390_interrupt_info *inti)
 		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 {