diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index d388629ab990..8f7281444551 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -324,8 +324,10 @@ struct arm_smmu_master_cfg {
 #define INVALID_SMENDX			-1
 #define __fwspec_cfg(fw) ((struct arm_smmu_master_cfg *)fw->iommu_priv)
 #define fwspec_smmu(fw)  (__fwspec_cfg(fw)->smmu)
+#define fwspec_smendx(fw, i) \
+	(i >= fw->num_ids ? INVALID_SMENDX : __fwspec_cfg(fw)->smendx[i])
 #define for_each_cfg_sme(fw, i, idx) \
-	for (i = 0; idx = __fwspec_cfg(fw)->smendx[i], i < fw->num_ids; ++i)
+	for (i = 0; idx = fwspec_smendx(fw, i), i < fw->num_ids; ++i)
 
 struct arm_smmu_device {
 	struct device			*dev;