[PATCH 1/1] KVM: Fix potentially recursively get kvm lock

[Sheng Yang <sheng@xxxxxxxxxxxxxxx>]

kvm_vm_ioctl_deassign_dev_irq() would potentially recursively get kvm->lock,
because it called kvm_deassigned_irq() which implicit hold kvm->lock by calling
deassign_host_irq().

Fix it by move kvm_deassign_irq() out of critial region. And add the missing
lock for deassign_guest_irq().

Reported-by: Alex Williamson <alex.williamson@xxxxxx>
Signed-off-by: Sheng Yang <sheng@xxxxxxxxxxxxxxx>
---
 virt/kvm/kvm_main.c |   14 +++++++-------
 1 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4d00942..3c69655 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -215,6 +215,8 @@ static void kvm_assigned_dev_ack_irq(struct kvm_irq_ack_notifier *kian)
 static void deassign_guest_irq(struct kvm *kvm,
 			       struct kvm_assigned_dev_kernel *assigned_dev)
 {
+	mutex_lock(&kvm->lock);
+
 	kvm_unregister_irq_ack_notifier(&assigned_dev->ack_notifier);
 	assigned_dev->ack_notifier.gsi = -1;
 
@@ -222,6 +224,8 @@ static void deassign_guest_irq(struct kvm *kvm,
 		kvm_free_irq_source_id(kvm, assigned_dev->irq_source_id);
 	assigned_dev->irq_source_id = -1;
 	assigned_dev->irq_requested_type &= ~(KVM_DEV_IRQ_GUEST_MASK);
+
+	mutex_unlock(&kvm->lock);
 }
 
 /* The function implicit hold kvm->lock mutex due to cancel_work_sync() */
@@ -558,20 +562,16 @@ static int kvm_vm_ioctl_deassign_dev_irq(struct kvm *kvm,
 					 struct kvm_assigned_irq
 					 *assigned_irq)
 {
-	int r = -ENODEV;
 	struct kvm_assigned_dev_kernel *match;
 
 	mutex_lock(&kvm->lock);
-
 	match = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head,
 				      assigned_irq->assigned_dev_id);
+	mutex_unlock(&kvm->lock);
 	if (!match)
-		goto out;
+		return -ENODEV;
 
-	r = kvm_deassign_irq(kvm, match, assigned_irq->flags);
-out:
-	mutex_unlock(&kvm->lock);
-	return r;
+	return kvm_deassign_irq(kvm, match, assigned_irq->flags);
 }
 
 static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
-- 
1.5.4.5

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