kunit: executor: Simplify string allocation handling

The alloc/copy code pattern is better consolidated to single kstrdup (and
kstrndup) calls instead. This gets rid of deprecated[1] strncpy() uses as
well. Replace one other strncpy() use with the more idiomatic strscpy().

Link: https://github.com/KSPP/linux/issues/90 [1]
Reviewed-by: David Gow <[e-mail]>
Signed-off-by: Kees Cook <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

lib/kunit/executor.c

···
 static int kunit_parse_glob_filter(struct kunit_glob_filter *parsed,
 				    const char *filter_glob)
 {
-	const int len = strlen(filter_glob);
 	const char *period = strchr(filter_glob, '.');
 
 	if (!period) {
-		parsed->suite_glob = kzalloc(len + 1, GFP_KERNEL);
+		parsed->suite_glob = kstrdup(filter_glob, GFP_KERNEL);
 		if (!parsed->suite_glob)
 			return -ENOMEM;
-
 		parsed->test_glob = NULL;
-		strcpy(parsed->suite_glob, filter_glob);
 		return 0;
 	}
 
-	parsed->suite_glob = kzalloc(period - filter_glob + 1, GFP_KERNEL);
+	parsed->suite_glob = kstrndup(filter_glob, period - filter_glob, GFP_KERNEL);
 	if (!parsed->suite_glob)
 		return -ENOMEM;
 
-	parsed->test_glob = kzalloc(len - (period - filter_glob) + 1, GFP_KERNEL);
+	parsed->test_glob = kstrdup(period + 1, GFP_KERNEL);
 	if (!parsed->test_glob) {
 		kfree(parsed->suite_glob);
 		return -ENOMEM;
 	}
-
-	strncpy(parsed->suite_glob, filter_glob, period - filter_glob);
-	strncpy(parsed->test_glob, period + 1, len - (period - filter_glob));
 
 	return 0;
 }

lib/kunit/executor_test.c

···
 
 	/* We normally never expect to allocate suites, hence the non-const cast. */
 	suite = kunit_kzalloc(test, sizeof(*suite), GFP_KERNEL);
-	strncpy((char *)suite->name, suite_name, sizeof(suite->name) - 1);
+	strscpy((char *)suite->name, suite_name, sizeof(suite->name));
 	suite->test_cases = test_cases;
 
 	return suite;