diff --git a/drivers/firmware/iscsi_ibft.c b/drivers/firmware/iscsi_ibft.c
index 7e12cbdf957c..daf42b5319e8 100644
--- a/drivers/firmware/iscsi_ibft.c
+++ b/drivers/firmware/iscsi_ibft.c
@@ -311,7 +311,10 @@ static ssize_t ibft_attr_show_nic(void *data, int type, char *buf)
 		str += sprintf_ipaddr(str, nic->ip_addr);
 		break;
 	case ISCSI_BOOT_ETH_SUBNET_MASK:
-		val = cpu_to_be32(~((1 << (32-nic->subnet_mask_prefix))-1));
+		if (nic->subnet_mask_prefix > 32)
+			val = cpu_to_be32(~0);
+		else
+			val = cpu_to_be32(~((1 << (32-nic->subnet_mask_prefix))-1));
 		str += sprintf(str, "%pI4", &val);
 		break;
 	case ISCSI_BOOT_ETH_PREFIX_LEN: