Sashiko reported that the irqchip index is not validated for PowerPC.
Add validation and reject out-of-range irqchip indexes to avoid indexing
past the routing table's chip array.

Fixes: de9ba2f36368 ("KVM: PPC: Support irq routing and irqfd for in-kernel MPIC")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/kvm/20260525051714.485D51F000E9@smtp.kernel.org/ (local)
Reviewed-by: Harsh Prateek Bora <redacted>
Signed-off-by: Yanfei Xu <redacted>
---
 arch/powerpc/kvm/mpic.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/mpic.c b/arch/powerpc/kvm/mpic.c
index 3070f36d9fb8..fb5f9e65e02e 100644
--- a/arch/powerpc/kvm/mpic.c
+++ b/arch/powerpc/kvm/mpic.c

@@ -1833,7 +1833,8 @@ int kvm_set_routing_entry(struct kvm *kvm,
 		e->set = mpic_set_irq;
 		e->irqchip.irqchip = ue->u.irqchip.irqchip;
 		e->irqchip.pin = ue->u.irqchip.pin;
-		if (e->irqchip.pin >= KVM_IRQCHIP_NUM_PINS)
+		if (e->irqchip.pin >= KVM_IRQCHIP_NUM_PINS ||
+		    e->irqchip.irqchip >= KVM_NR_IRQCHIPS)
 			goto out;
 		break;
 	case KVM_IRQ_ROUTING_MSI:

-- 
2.20.1