diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index d9c748b6f9e452..7f9824b0609e79 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -144,7 +144,7 @@ dmar_alloc_pci_notify_info(struct pci_dev *dev, unsigned long event)
 		for (tmp = dev; tmp; tmp = tmp->bus->self)
 			level++;
 
-	size = sizeof(*info) + level * sizeof(struct acpi_dmar_pci_path);
+	size = sizeof(*info) + level * sizeof(info->path[0]);
 	if (size <= sizeof(dmar_pci_notify_info_buf)) {
 		info = (struct dmar_pci_notify_info *)dmar_pci_notify_info_buf;
 	} else {