[PATCH] KVM: arm/arm64: Fix KVM_VGIC_V3_ADDR_TYPE_REDIST read

[Eric Auger]

When reading the base address of the a REDIST region
through KVM_VGIC_V3_ADDR_TYPE_REDIST we expect the
redistributor region list to be populated with a single
element.

However list_first_entry() expects the list to be non empty.
Instead we should use list_first_entry_or_null which effectively
returns NULL if the list is empty.

Fixes: dbd9733ab674 ("KVM: arm/arm64: Replace the single rdist region by a 
list")
Cc: <sta...@vger.kernel.org> # v4.18+
Signed-off-by: Eric Auger <eric.au...@redhat.com>
Reported-by: Gavin Shan <gs...@redhat.com>
---
 arch/arm64/kvm/vgic/vgic-kvm-device.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c 
b/arch/arm64/kvm/vgic/vgic-kvm-device.c
index 44419679f91a..5eaede3e3b5a 100644
--- a/arch/arm64/kvm/vgic/vgic-kvm-device.c
+++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c
@@ -87,8 +87,8 @@ int kvm_vgic_addr(struct kvm *kvm, unsigned long type, u64 
*addr, bool write)
                        r = vgic_v3_set_redist_base(kvm, 0, *addr, 0);
                        goto out;
                }
-               rdreg = list_first_entry(&vgic->rd_regions,
-                                        struct vgic_redist_region, list);
+               rdreg = list_first_entry_or_null(&vgic->rd_regions,
+                                                struct vgic_redist_region, 
list);
                if (!rdreg)
                        addr_ptr = &undef_value;
                else
-- 
2.26.3