selinux: new helper - selinux_add_opt()

the guts of the loop in selinux_parse_opts_str() - takes one
(already recognized) option and adds it to growing selinux_mnt_opts.
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

security/selinux/hooks.c

@@ -984,97 +984,77 @@ static int selinux_sb_clone_mnt_opts(const struct super_block *oldsb,
 	return rc;
 }
 
+static int selinux_add_opt(int token, const char *s, void **mnt_opts)
+{
+	struct selinux_mnt_opts *opts = *mnt_opts;
+
+	if (!opts) {
+		opts = kzalloc(sizeof(struct selinux_mnt_opts), GFP_KERNEL);
+		if (!opts)
+			return -ENOMEM;
+		*mnt_opts = opts;
+	}
+	if (!s)
+		return -ENOMEM;
+	switch (token) {
+	case Opt_context:
+		if (opts->context || opts->defcontext)
+			goto Einval;
+		opts->context = s;
+		break;
+	case Opt_fscontext:
+		if (opts->fscontext)
+			goto Einval;
+		opts->fscontext = s;
+		break;
+	case Opt_rootcontext:
+		if (opts->rootcontext)
+			goto Einval;
+		opts->rootcontext = s;
+		break;
+	case Opt_defcontext:
+		if (opts->context || opts->defcontext)
+			goto Einval;
+		opts->defcontext = s;
+		break;
+	}
+	return 0;
+Einval:
+	pr_warn(SEL_MOUNT_FAIL_MSG);
+	kfree(s);
+	return -EINVAL;
+}
+
 static int selinux_parse_opts_str(char *options,
 				  void **mnt_opts)
 {
-	struct selinux_mnt_opts *opts = *mnt_opts;
 	char *p;
-	int rc;
 
 	/* Standard string-based options. */
 	while ((p = strsep(&options, "|")) != NULL) {
-		int token;
+		int token, rc;
 		substring_t args[MAX_OPT_ARGS];
+		const char *arg;
 
 		if (!*p)
 			continue;
 
 		token = match_token(p, tokens, args);
 
-		if (!opts) {
-			opts = kzalloc(sizeof(struct selinux_mnt_opts), GFP_KERNEL);
-			if (!opts)
-				return -ENOMEM;
-		}
-
-		switch (token) {
-		case Opt_context:
-			if (opts->context || opts->defcontext) {
-				rc = -EINVAL;
-				pr_warn(SEL_MOUNT_FAIL_MSG);
-				goto out_err;
-			}
-			opts->context = match_strdup(&args[0]);
-			if (!opts->context) {
-				rc = -ENOMEM;
-				goto out_err;
-			}
-			break;
-
-		case Opt_fscontext:
-			if (opts->fscontext) {
-				rc = -EINVAL;
-				pr_warn(SEL_MOUNT_FAIL_MSG);
-				goto out_err;
-			}
-			opts->fscontext = match_strdup(&args[0]);
-			if (!opts->fscontext) {
-				rc = -ENOMEM;
-				goto out_err;
-			}
-			break;
-
-		case Opt_rootcontext:
-			if (opts->rootcontext) {
-				rc = -EINVAL;
-				pr_warn(SEL_MOUNT_FAIL_MSG);
-				goto out_err;
-			}
-			opts->rootcontext = match_strdup(&args[0]);
-			if (!opts->rootcontext) {
-				rc = -ENOMEM;
-				goto out_err;
-			}
-			break;
-
-		case Opt_defcontext:
-			if (opts->context || opts->defcontext) {
-				rc = -EINVAL;
-				pr_warn(SEL_MOUNT_FAIL_MSG);
-				goto out_err;
-			}
-			opts->defcontext = match_strdup(&args[0]);
-			if (!opts->defcontext) {
-				rc = -ENOMEM;
-				goto out_err;
+		if (token == Opt_labelsupport)	/* eaten and completely ignored */
+			continue;
+		arg = match_strdup(&args[0]);
+		rc = selinux_add_opt(token, arg, mnt_opts);
+		if (unlikely(rc)) {
+			kfree(arg);
+			if (*mnt_opts) {
+				selinux_free_mnt_opts(*mnt_opts);
+				*mnt_opts = NULL;
 			}
-			break;
-		case Opt_labelsupport:
-			break;
-		default:
-			rc = -EINVAL;
-			pr_warn("SELinux:  unknown mount option\n");
-			goto out_err;
-
+			return rc;
 		}
 	}
-	*mnt_opts = opts;
 	return 0;
-
-out_err:
-	if (opts)
-		selinux_free_mnt_opts(opts);
-	return rc;
 }
 
 static int show_sid(struct seq_file *m, u32 sid)