linux-kernel - [PATCH AUTOSEL for 4.14 030/100] KVM: arm/arm64: Fix spinlock acquisition in vgic_set

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Date:   Sun, 28 Jan 2018 22:26:17 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Marc Zyngier <marc.zyngier@....com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.14 030/100] KVM: arm/arm64: Fix spinlock
 acquisition in vgic_set_owner

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@...rosoft.com>
---
 virt/kvm/arm/vgic/vgic.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index fed717e07938..da53c6e7d688 100644
--- 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_vcpu *vcpu, unsigned int virt_irq)
 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 *vcpu, unsigned int intid, void *owner)
 		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;
 }
-- 
2.11.0