diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 8189cb6..7abc5c8 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -346,6 +346,7 @@ static long vfio_pci_ioctl(void *device_data,
 
 		if (!(hdr.flags & VFIO_IRQ_SET_DATA_NONE)) {
 			size_t size;
+			int max = vfio_pci_get_irq_count(vdev, hdr.index);
 
 			if (hdr.flags & VFIO_IRQ_SET_DATA_BOOL)
 				size = sizeof(uint8_t);
@@ -355,7 +356,7 @@ static long vfio_pci_ioctl(void *device_data,
 				return -EINVAL;
 
 			if (hdr.argsz - minsz < hdr.count * size ||
-			    hdr.count > vfio_pci_get_irq_count(vdev, hdr.index))
+			    hdr.start >= max || hdr.start + hdr.count > max)
 				return -EINVAL;
 
 			data = memdup_user((void __user *)(arg + minsz),