[PATCH v2 3/4] KVM: arm64: vgic: Reject out-of-range GICv5 PPI IDs

[Sascha Bischoff <Sascha.Bischoff@arm.com>]

GICv5 supports up to 128 PPIs, but KVM currently implements only the
first 64, which contain the architected PPIs it supports.

An encoded PPI with an ID outside that range passes irq_is_ppi(),
which only checks the encoded interrupt type. vgic_get_vcpu_irq()
therefore looks it up in private_irqs[], where array_index_nospec()
clamps the out-of-range index to zero and aliases PPI 0.

Include the supported PPI range in irq_is_ppi() so that KVM interfaces
reject unsupported PPIs. Also reject an out-of-range PPI in the lookup
as a safeguard against callers bypassing the predicate.

Fixes: 4d591252bacb ("KVM: arm64: gic-v5: Implement PPI interrupt injection")
Fixes: eb8bce08ecb1 ("KVM: arm64: gic: Introduce interrupt type helpers")
Link: https://sashiko.dev/#/patchset/20260724104819.1296803-1-sascha.bischoff@arm.com?part=27
Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
---
 arch/arm64/kvm/vgic/vgic.c | 2 ++
 include/kvm/arm_vgic.h     | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index 352d52bd6315c..b25303d9919fd 100644
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c
@@ -118,6 +118,8 @@ struct vgic_irq *vgic_get_vcpu_irq(struct kvm_vcpu *vcpu, u32 intid)
 		switch (type) {
 		case KVM_DEV_TYPE_ARM_VGIC_V5:
 			intid = vgic_v5_get_hwirq_id(intid);
+			if (intid >= VGIC_V5_NR_PRIVATE_IRQS)
+				return NULL;
 			intid = array_index_nospec(intid, VGIC_V5_NR_PRIVATE_IRQS);
 			break;
 		default:
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index cefddc9c621de..1a549cceecbec 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -65,6 +65,8 @@
 		switch (t) {						\
 		case KVM_DEV_TYPE_ARM_VGIC_V5:				\
 			__ret = is_v5_type(GICV5_HWIRQ_TYPE_PPI, (i));	\
+			__ret &= FIELD_GET(GICV5_HWIRQ_ID, (i)) <	\
+				 VGIC_V5_NR_PRIVATE_IRQS;		\
 			break;						\
 		default:						\
 			__ret  = (i) >= VGIC_NR_SGIS;			\
-- 
2.34.1