selinux: fix potential memleak in selinux_add_opt()

This patch try to fix potential memleak in error branch.

Fixes: ba641862 ("selinux: new helper - selinux_add_opt()")
Signed-off-by: Bernard Zhao <bernard@vivo.com>
[PM: tweak the subject line, add Fixes tag]
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/hooks.c

@@ -970,18 +970,22 @@ static int selinux_sb_clone_mnt_opts(const struct super_block *oldsb,
 static int selinux_add_opt(int token, const char *s, void **mnt_opts)
 {
 	struct selinux_mnt_opts *opts = *mnt_opts;
+	bool is_alloc_opts = false;
 
 	if (token == Opt_seclabel)	/* eaten and completely ignored */
 		return 0;
 
+	if (!s)
+		return -ENOMEM;
+
 	if (!opts) {
 		opts = kzalloc(sizeof(struct selinux_mnt_opts), GFP_KERNEL);
 		if (!opts)
 			return -ENOMEM;
 		*mnt_opts = opts;
+		is_alloc_opts = true;
 	}
-	if (!s)
-		return -ENOMEM;
+
 	switch (token) {
 	case Opt_context:
 		if (opts->context || opts->defcontext)
@@ -1006,6 +1010,10 @@ static int selinux_add_opt(int token, const char *s, void **mnt_opts)
 	}
 	return 0;
 Einval:
+	if (is_alloc_opts) {
+		kfree(opts);
+		*mnt_opts = NULL;
+	}
 	pr_warn(SEL_MOUNT_FAIL_MSG);
 	return -EINVAL;
 }