KVM: Fix assigned devices circular locking dependency

kvm->slots_lock is outer to kvm->lock, so take slots_lock
in kvm_vm_ioctl_assign_device() before taking kvm->lock,
rather than taking it in kvm_iommu_map_memslots().

Cc: stable@kernel.org
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d9bbb20f230f..29a667ce35b0 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -466,6 +466,7 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
         struct kvm_assigned_dev_kernel *match;
         struct pci_dev *dev;
 
+        down_read(&kvm->slots_lock);
         mutex_lock(&kvm->lock);
 
         match = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head,
@@ -527,6 +528,7 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
 
 out:
         mutex_unlock(&kvm->lock);
+        up_read(&kvm->slots_lock);
         return r;
 out_list_del:
         list_del(&match->list);
@@ -538,6 +540,7 @@ out_put:
 out_free:
         kfree(match);
         mutex_unlock(&kvm->lock);
+        up_read(&kvm->slots_lock);
         return r;
 }
 #endif