KVM: arm/arm64: Fix KVM_VGIC_V3_ADDR_TYPE_REDIST read

BugLink: https://bugs.launchpad.net/bugs/1929455
commit 94ac0835391efc1a30feda6fc908913ec012951e upstream.

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: <Stable@vger.kernel.org> # v4.18+
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reported-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210412150034.29185-1-eric.auger@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c
index 44419679f91ad724d637abd7719c63405d005d76..5eaede3e3b5a558db69b14f646f8c44e626acddf 100644 (file)
--- 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