linux-kernel - [PATCH for-stable-5.4] KVM: arm/arm64: Fix KVM_VGIC_V3_ADDR_TYPE

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Message-Id: <20210621124232.793383-1-eric.auger@redhat.com>
Date:   Mon, 21 Jun 2021 14:42:32 +0200
From:   Eric Auger <eric.auger@...hat.com>
To:     eric.auger.pro@...il.com, eric.auger@...hat.com,
        stable@...r.kernel.org, maz@...nel.org,
        linux-kernel@...r.kernel.org, kvmarm@...ts.cs.columbia.edu
Subject: [PATCH for-stable-5.4] 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: <Stable@...r.kernel.org> # v5.4
Signed-off-by: Eric Auger <eric.auger@...hat.com>
Reported-by: Gavin Shan <gshan@...hat.com>
Signed-off-by: Marc Zyngier <maz@...nel.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 44419679f91a..5eaede3e3b5a 100644
--- a/virt/kvm/arm/vgic/vgic-kvm-device.c
+++ b/virt/kvm/arm/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