linux-kernel - [PATCH 4.14 088/159] KVM: arm/arm64: Fix spinlock acquisition in vgic_set

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Message-Id: <20180223170754.163578815@linuxfoundation.org>
Date:   Fri, 23 Feb 2018 19:26:36 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, James Morse <james.morse@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.14 088/159] KVM: arm/arm64: Fix spinlock acquisition in vgic_set_owner

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

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

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


[ Upstream commit 7465894e90e5a47e0e52aa5f1f708653fc40020f ]

vgic_set_owner acquires the irq lock without disabling interrupts,
resulting in a lockdep splat (an interrupt could fire and result
in the same lock being taken if the same virtual irq is to be
injected).

In practice, it is almost impossible to trigger this bug, but
better safe than sorry. Convert the lock acquisition to a
spin_lock_irqsave() and keep lockdep happy.

Reported-by: James Morse <james.morse@....com>
Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Christoffer Dall <christoffer.dall@...aro.org>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 virt/kvm/arm/vgic/vgic.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -454,6 +454,7 @@ int kvm_vgic_unmap_phys_irq(struct kvm_v
 int kvm_vgic_set_owner(struct kvm_vcpu *vcpu, unsigned int intid, void *owner)
 {
 	struct vgic_irq *irq;
+	unsigned long flags;
 	int ret = 0;
 
 	if (!vgic_initialized(vcpu->kvm))
@@ -464,12 +465,12 @@ int kvm_vgic_set_owner(struct kvm_vcpu *
 		return -EINVAL;
 
 	irq = vgic_get_irq(vcpu->kvm, vcpu, intid);
-	spin_lock(&irq->irq_lock);
+	spin_lock_irqsave(&irq->irq_lock, flags);
 	if (irq->owner && irq->owner != owner)
 		ret = -EEXIST;
 	else
 		irq->owner = owner;
-	spin_unlock(&irq->irq_lock);
+	spin_unlock_irqrestore(&irq->irq_lock, flags);
 
 	return ret;
 }