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

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: <redacted> # v4.19
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reported-by: Gavin Shan <redacted>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210412150034.29185-1-eric.auger@redhat.com
---
 virt/kvm/arm/vgic/vgic-kvm-device.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-kvm-device.c b/virt/kvm/arm/vgic/vgic-kvm-device.c
index 6ada2432e37c..71d92096776e 100644
--- a/virt/kvm/arm/vgic/vgic-kvm-device.c
+++ b/virt/kvm/arm/vgic/vgic-kvm-device.c

@@ -95,8 +95,8 @@ 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

Hi,

On 6/21/21 2:18 PM, Eric Auger wrote:

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: <redacted> # v4.19
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reported-by: Gavin Shan <redacted>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210412150034.29185-1-eric.auger@redhat.com

Maybe I should I prefixed the patch with [stable-4.19]. This is already
on master and in various stable but did not apply on 4.19

Thanks

Eric

Hi,

On 6/21/21 2:18 PM, Eric Auger wrote:

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: <redacted> # v4.19
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reported-by: Gavin Shan <redacted>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210412150034.29185-1-eric.auger@redhat.com

so I have resent with the [PATCH for-stable-4.19] prefix.
Please ignore that patch and sorry for the mess.

Thanks

Eric