linux-kernel - [PATCH 3.10 42/53] KVM: s390: floating irqs: fix user triggerable endless loop

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Message-Id: <20150304054616.976587208@linuxfoundation.org>
Date:	Tue,  3 Mar 2015 22:06:45 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Dominik Dingel <dingel@...ux.vnet.ibm.com>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	David Hildenbrand <dahi@...ux.vnet.ibm.com>,
	Christian Borntraeger <borntraeger@...ibm.com>
Subject: [PATCH 3.10 42/53] KVM: s390: floating irqs: fix user triggerable endless loop

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Hildenbrand <dahi@...ux.vnet.ibm.com>

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@...ux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@...ibm.com>
Signed-off-by: David Hildenbrand <dahi@...ux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/s390/kvm/interrupt.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -736,6 +736,8 @@ int kvm_s390_inject_vm(struct kvm *kvm,
 		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 {


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