net: remove newlines in NL_SET_ERR_MSG_MOD

The NL_SET_ERR_MSG_MOD macro is used to report a string describing an
error message to userspace via the netlink extended ACK structure. It
should not have a trailing newline.

Add a cocci script which catches cases where the newline marker is
present. Using this script, fix the handful of cases which accidentally
included a trailing new line.

I couldn't figure out a way to get a patch mode working, so this script
only implements context, report, and org.

Signed-off-by: Jacob Keller <[e-mail]>
Cc: Jakub Kicinski <[e-mail]>
Cc: Andy Whitcroft <[e-mail]>
Cc: Joe Perches <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/mellanox/mlx5/core/en_tc.c

···
 		if (IS_ERR(priv->fs.tc.t)) {
 			mutex_unlock(&priv->fs.tc.t_lock);
 			NL_SET_ERR_MSG_MOD(extack,
-					   "Failed to create tc offload table\n");
+					   "Failed to create tc offload table");
 			netdev_err(priv->netdev,
 				   "Failed to create tc offload table\n");
 			return PTR_ERR(priv->fs.tc.t);

drivers/net/ethernet/mscc/ocelot_tc.c

···
 
 		if (priv->tc.police_id && priv->tc.police_id != f->cookie) {
 			NL_SET_ERR_MSG_MOD(extack,
-					   "Only one policer per port is supported\n");
+					   "Only one policer per port is supported");
 			return -EEXIST;
 		}
 
···
 
 		err = ocelot_port_policer_add(ocelot, port, &pol);
 		if (err) {
-			NL_SET_ERR_MSG_MOD(extack, "Could not add policer\n");
+			NL_SET_ERR_MSG_MOD(extack, "Could not add policer");
 			return err;
 		}
 
···
 		err = ocelot_port_policer_del(ocelot, port);
 		if (err) {
 			NL_SET_ERR_MSG_MOD(extack,
-					   "Could not delete policer\n");
+					   "Could not delete policer");
 			return err;
 		}
 		priv->tc.police_id = 0;

net/bridge/br_mrp_netlink.c

···
 	int err;
 
 	if (br->stp_enabled != BR_NO_STP) {
-		NL_SET_ERR_MSG_MOD(extack, "MRP can't be enabled if STP is already enabled\n");
+		NL_SET_ERR_MSG_MOD(extack, "MRP can't be enabled if STP is already enabled");
 		return -EINVAL;
 	}
 

net/bridge/br_stp_if.c

···
 
 	if (br_mrp_enabled(br)) {
 		NL_SET_ERR_MSG_MOD(extack,
-				   "STP can't be enabled if MRP is already enabled\n");
+				   "STP can't be enabled if MRP is already enabled");
 		return -EINVAL;
 	}
 

net/dsa/slave.c

···
 
 	if (!ds->ops->port_policer_add) {
 		NL_SET_ERR_MSG_MOD(extack,
-				   "Policing offload not implemented\n");
+				   "Policing offload not implemented");
 		return -EOPNOTSUPP;
 	}
 
 	if (!ingress) {
 		NL_SET_ERR_MSG_MOD(extack,
-				   "Only supported on ingress qdisc\n");
+				   "Only supported on ingress qdisc");
 		return -EOPNOTSUPP;
 	}
 
···
 	list_for_each_entry(mall_tc_entry, &p->mall_tc_list, list) {
 		if (mall_tc_entry->type == DSA_PORT_MALL_POLICER) {
 			NL_SET_ERR_MSG_MOD(extack,
-					   "Only one port policer allowed\n");
+					   "Only one port policer allowed");
 			return -EEXIST;
 		}
 	}

scripts/coccinelle/misc/newline_in_nl_msg.cocci

···
+// SPDX-License-Identifier: GPL-2.0-only
+///
+/// Catch strings ending in newline with GENL_SET_ERR_MSG, NL_SET_ERR_MSG,
+/// NL_SET_ERR_MSG_MOD.
+///
+// Confidence: Very High
+// Copyright: (C) 2020 Intel Corporation
+// URL: http://coccinelle.lip6.fr/
+// Options: --no-includes --include-headers
+
+virtual context
+virtual org
+virtual report
+
+@r depends on context || org || report@
+expression e;
+constant m;
+position p;
+@@
+  \(GENL_SET_ERR_MSG\|NL_SET_ERR_MSG\|NL_SET_ERR_MSG_MOD\)(e,m@p)
+
+@script:python@
+m << r.m;
+@@
+
+if not m.endswith("\\n\""):
+	cocci.include_match(False)
+
+@r1 depends on r@
+identifier fname;
+expression r.e;
+constant r.m;
+position r.p;
+@@
+  fname(e,m@p)
+
+//----------------------------------------------------------
+//  For context mode
+//----------------------------------------------------------
+
+@depends on context && r@
+identifier r1.fname;
+expression r.e;
+constant r.m;
+@@
+* fname(e,m)
+
+//----------------------------------------------------------
+//  For org mode
+//----------------------------------------------------------
+
+@script:python depends on org@
+fname << r1.fname;
+m << r.m;
+p << r.p;
+@@
+
+if m.endswith("\\n\""):
+	msg="WARNING avoid newline at end of message in %s" % (fname)
+	msg_safe=msg.replace("[","@(").replace("]",")")
+	coccilib.org.print_todo(p[0], msg_safe)
+
+//----------------------------------------------------------
+//  For report mode
+//----------------------------------------------------------
+
+@script:python depends on report@
+fname << r1.fname;
+m << r.m;
+p << r.p;
+@@
+
+if m.endswith("\\n\""):
+	msg="WARNING avoid newline at end of message in %s" % (fname)
+	coccilib.report.print_report(p[0], msg)