KVM: arm/arm64: vgic: Fix deadlock on error handling

commit 1193e6aeecb36c74c48c7cd0f641acbbed9ddeef upstream.

Dmitry Vyukov reported that the syzkaller fuzzer triggered a
deadlock in the vgic setup code when an error was detected, as
the cleanup code tries to take a lock that is already held by
the setup code.

The fix is to avoid retaking the lock when cleaning up, by
telling the cleanup function that we already hold it.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 13 insertions, 9 deletions

diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index 8cebfbc19e90..539d3f5cb619 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -268,15 +268,11 @@ static void kvm_vgic_dist_destroy(struct kvm *kvm)
 {
         struct vgic_dist *dist = &kvm->arch.vgic;
 
-        mutex_lock(&kvm->lock);
-
         dist->ready = false;
         dist->initialized = false;
 
         kfree(dist->spis);
         dist->nr_spis = 0;
-
-        mutex_unlock(&kvm->lock);
 }
 
 void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu)
@@ -286,7 +282,8 @@ void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu)
         INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
 }
 
-void kvm_vgic_destroy(struct kvm *kvm)
+/* To be called with kvm->lock held */
+static void __kvm_vgic_destroy(struct kvm *kvm)
 {
         struct kvm_vcpu *vcpu;
         int i;
@@ -297,6 +294,13 @@ void kvm_vgic_destroy(struct kvm *kvm)
                 kvm_vgic_vcpu_destroy(vcpu);
 }
 
+void kvm_vgic_destroy(struct kvm *kvm)
+{
+        mutex_lock(&kvm->lock);
+        __kvm_vgic_destroy(kvm);
+        mutex_unlock(&kvm->lock);
+}
+
 /**
  * vgic_lazy_init: Lazy init is only allowed if the GIC exposed to the guest
  * is a GICv2. A GICv3 must be explicitly initialized by the guest using the
@@ -348,6 +352,10 @@ int kvm_vgic_map_resources(struct kvm *kvm)
                 ret = vgic_v2_map_resources(kvm);
         else
                 ret = vgic_v3_map_resources(kvm);
+
+        if (ret)
+                __kvm_vgic_destroy(kvm);
+
 out:
         mutex_unlock(&kvm->lock);
         return ret;
diff --git a/virt/kvm/arm/vgic/vgic-v2.c b/virt/kvm/arm/vgic/vgic-v2.c
index 9bab86757fa4..834137e7b83f 100644
--- a/virt/kvm/arm/vgic/vgic-v2.c
+++ b/virt/kvm/arm/vgic/vgic-v2.c
@@ -293,8 +293,6 @@ int vgic_v2_map_resources(struct kvm *kvm)
         dist->ready = true;
 
 out:
-        if (ret)
-                kvm_vgic_destroy(kvm);
         return ret;
 }
 
diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index 5c9f9745e6ca..e6b03fd8c374 100644
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c
@@ -302,8 +302,6 @@ int vgic_v3_map_resources(struct kvm *kvm)
         dist->ready = true;
 
 out:
-        if (ret)
-                kvm_vgic_destroy(kvm);
         return ret;
 }