selftests/bpf: Free strdup memory in test_sockmap

The strdup() function returns a pointer to a new string which is a
duplicate of the string "ptr". Memory for the new string is obtained
with malloc(), and need to be freed with free().

This patch adds these missing "free(ptr)" in check_whitelist() and
check_blacklist() to avoid memory leaks in test_sockmap.c.
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/b76f2f4c550aebe4ab8ea73d23c4cbe4f06ea996.1714374022.git.tanggeliang@kylinos.cn

tools/testing/selftests/bpf/test_sockmap.c

@@ -1887,10 +1887,13 @@ static int check_whitelist(struct _test *t, struct sockmap_options *opt)
 	while (entry) {
 		if ((opt->prepend && strstr(opt->prepend, entry) != 0) ||
 		    strstr(opt->map, entry) != 0 ||
-		    strstr(t->title, entry) != 0)
+		    strstr(t->title, entry) != 0) {
+			free(ptr);
 			return 0;
+		}
 		entry = strtok(NULL, ",");
 	}
+	free(ptr);
 	return -EINVAL;
 }
 
@@ -1907,10 +1910,13 @@ static int check_blacklist(struct _test *t, struct sockmap_options *opt)
 	while (entry) {
 		if ((opt->prepend && strstr(opt->prepend, entry) != 0) ||
 		    strstr(opt->map, entry) != 0 ||
-		    strstr(t->title, entry) != 0)
+		    strstr(t->title, entry) != 0) {
+			free(ptr);
 			return 0;
+		}
 		entry = strtok(NULL, ",");
 	}
+	free(ptr);
 	return -EINVAL;
 }