ubifs: Add CONFIG_UBIFS_FS_SECURITY to disable/enable security labels

When write syscall is called, every time security label is searched to
determine that file's privileges should be changed.
If LSM(Linux Security Model) is not used, this is useless.

So introduce CONFIG_UBIFS_SECURITY to disable security labels. it's default
value is "y".

Signed-off-by: Hyunchul Lee <cheol.lee@lge.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

fs/ubifs/Kconfig

@@ -61,3 +61,16 @@ config UBIFS_FS_ENCRYPTION
 	  feature is similar to ecryptfs, but it is more memory
 	  efficient since it avoids caching the encrypted and
 	  decrypted pages in the page cache.
+
+config UBIFS_FS_SECURITY
+	bool "UBIFS Security Labels"
+	depends on UBIFS_FS
+	default y
+	help
+	  Security labels provide an access control facility to support Linux
+	  Security Models (LSMs) accepted by AppArmor, SELinux, Smack and TOMOYO
+	  Linux. This option enables an extended attribute handler for file
+	  security labels in the ubifs filesystem, so that it requires enabling
+	  the extended attribute support in advance.
+
+	  If you are not using a security module, say N.

fs/ubifs/ubifs.h

@@ -1756,13 +1756,23 @@ int ubifs_check_dir_empty(struct inode *dir);
 /* xattr.c */
 extern const struct xattr_handler *ubifs_xattr_handlers[];
 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size);
-int ubifs_init_security(struct inode *dentry, struct inode *inode,
-			const struct qstr *qstr);
 int ubifs_xattr_set(struct inode *host, const char *name, const void *value,
 		    size_t size, int flags);
 ssize_t ubifs_xattr_get(struct inode *host, const char *name, void *buf,
 			size_t size);
 
+#ifdef CONFIG_UBIFS_FS_SECURITY
+extern int ubifs_init_security(struct inode *dentry, struct inode *inode,
+			const struct qstr *qstr);
+#else
+static inline int ubifs_init_security(struct inode *dentry,
+			struct inode *inode, const struct qstr *qstr)
+{
+	return 0;
+}
+#endif
+
+
 /* super.c */
 struct inode *ubifs_iget(struct super_block *sb, unsigned long inum);
 

fs/ubifs/xattr.c

@@ -559,6 +559,7 @@ out_free:
 	return err;
 }
 
+#ifdef CONFIG_UBIFS_FS_SECURITY
 static int init_xattrs(struct inode *inode, const struct xattr *xattr_array,
 		      void *fs_info)
 {
@@ -599,6 +600,7 @@ int ubifs_init_security(struct inode *dentry, struct inode *inode,
 	}
 	return err;
 }
+#endif
 
 static int xattr_get(const struct xattr_handler *handler,
 			   struct dentry *dentry, struct inode *inode,
@@ -639,15 +641,19 @@ static const struct xattr_handler ubifs_trusted_xattr_handler = {
 	.set = xattr_set,
 };
 
+#ifdef CONFIG_UBIFS_FS_SECURITY
 static const struct xattr_handler ubifs_security_xattr_handler = {
 	.prefix = XATTR_SECURITY_PREFIX,
 	.get = xattr_get,
 	.set = xattr_set,
 };
+#endif
 
 const struct xattr_handler *ubifs_xattr_handlers[] = {
 	&ubifs_user_xattr_handler,
 	&ubifs_trusted_xattr_handler,
+#ifdef CONFIG_UBIFS_FS_SECURITY
 	&ubifs_security_xattr_handler,
+#endif
 	NULL
 };