src: avoid leak parsing command line arguemnts in "nl-{class,qdisc}-add"

"id" could be overwritten, this causes coverity warnings. While not
severe, fix the coverity warnings by using _nl_clear_free().

Also use _nl_auto_free to release the memory.

  Error: CLANG_WARNING: [#def79]
  libnl-3.9.0/src/nl-class-add.c:73:7: warning[unix.Malloc]: Potential leak of memory pointed to by 'id'
  #   71|
  #   72|   	for (;;) {
  #   73|-> 		int c, optidx = 0;
  #   74|   		enum {
  #   75|   			ARG_UPDATE = 257,

  Error: GCC_ANALYZER_WARNING (CWE-401): [#def80]
  libnl-3.9.0/src/nl-class-add.c: scope_hint: In function ‘main’
  libnl-3.9.0/src/nl-class-add.c:109:32: warning[-Wanalyzer-malloc-leak]: leak of ‘id’
  #  107|   		case 'd': nl_cli_tc_parse_dev(tc, link_cache, optarg); break;
  #  108|   		case 'p': nl_cli_tc_parse_parent(tc, optarg); break;
  #  109|-> 		case 'i': id = strdup(optarg); break;
  #  110|   		case ARG_UPDATE: flags = NLM_F_CREATE; break;
  #  111|   		case ARG_UPDATE_ONLY: flags = 0; break;

Author: thom311

src/nl-class-add.c

@@ -59,7 +59,8 @@ int main(int argc, char *argv[])
 	struct nl_cli_tc_module *tm;
 	struct rtnl_tc_ops *ops;
 	int err, flags = NLM_F_CREATE | NLM_F_EXCL;
-	char *kind, *id = NULL;
+	const char *kind;
+	_nl_auto_free char *id = NULL;
 
 	sock = nl_cli_alloc_socket();
 	nl_cli_connect(sock, NETLINK_ROUTE);
@@ -106,7 +107,7 @@ int main(int argc, char *argv[])
 		case 'v': nl_cli_print_version(); break;
 		case 'd': nl_cli_tc_parse_dev(tc, link_cache, optarg); break;
 		case 'p': nl_cli_tc_parse_parent(tc, optarg); break;
-		case 'i': id = strdup(optarg); break;
+		case 'i': _nl_clear_free(&id); id = strdup(optarg); break;
 		case ARG_UPDATE: flags = NLM_F_CREATE; break;
 		case ARG_UPDATE_ONLY: flags = 0; break;
 		case ARG_MTU: nl_cli_tc_parse_mtu(tc, optarg); break;
@@ -127,7 +128,6 @@ int main(int argc, char *argv[])
 
 	if (id) {
 		nl_cli_tc_parse_handle(tc, id, 1);
-		free(id);
 	}
 
 	kind = argv[optind++];

src/nl-qdisc-add.c

@@ -56,7 +56,8 @@ int main(int argc, char *argv[])
 	struct nl_cli_tc_module *tm;
 	struct rtnl_tc_ops *ops;
 	int err, flags = NLM_F_CREATE | NLM_F_EXCL;
-	char *kind, *id = NULL;
+	const char *kind;
+	_nl_auto_free char *id = NULL;
 
 	sock = nl_cli_alloc_socket();
 	nl_cli_connect(sock, NETLINK_ROUTE);
@@ -99,7 +100,7 @@ int main(int argc, char *argv[])
 		case 'v': nl_cli_print_version(); break;
 		case 'd': nl_cli_tc_parse_dev(tc, link_cache, optarg); break;
 		case 'p': nl_cli_tc_parse_parent(tc, optarg); break;
-		case 'i': id = strdup(optarg); break;
+		case 'i': _nl_clear_free(&id); id = strdup(optarg); break;
 		case ARG_UPDATE: flags = NLM_F_CREATE; break;
 		case ARG_REPLACE: flags = NLM_F_CREATE | NLM_F_REPLACE; break;
 		case ARG_UPDATE_ONLY: flags = 0; break;
@@ -118,7 +119,6 @@ int main(int argc, char *argv[])
 
 	if (id) {
 		nl_cli_tc_parse_handle(tc, id, 1);
-		free(id);
 	}
 
 	kind = argv[optind++];