LSM: Add security_path_chroot().

This patch allows pathname based LSM modules to check chroot() operations.

This hook is used by TOMOYO.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/include/linux/security.h b/include/linux/security.h
index c8a584c..ed0faea 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -459,6 +459,10 @@
  *	@uid contains new owner's ID.
  *	@gid contains new group's ID.
  *	Return 0 if permission is granted.
+ * @path_chroot:
+ *	Check for permission to change root directory.
+ *	@path contains the path structure.
+ *	Return 0 if permission is granted.
  * @inode_readlink:
  *	Check the permission to read the symbolic link.
  *	@dentry contains the dentry structure for the file link.
@@ -1503,6 +1507,7 @@
 	int (*path_chmod) (struct dentry *dentry, struct vfsmount *mnt,
 			   mode_t mode);
 	int (*path_chown) (struct path *path, uid_t uid, gid_t gid);
+	int (*path_chroot) (struct path *path);
 #endif
 
 	int (*inode_alloc_security) (struct inode *inode);
@@ -2970,6 +2975,7 @@
 int security_path_chmod(struct dentry *dentry, struct vfsmount *mnt,
 			mode_t mode);
 int security_path_chown(struct path *path, uid_t uid, gid_t gid);
+int security_path_chroot(struct path *path);
 #else	/* CONFIG_SECURITY_PATH */
 static inline int security_path_unlink(struct path *dir, struct dentry *dentry)
 {
@@ -3031,6 +3037,11 @@
 {
 	return 0;
 }
+
+static inline int security_path_chroot(struct path *path)
+{
+	return 0;
+}
 #endif	/* CONFIG_SECURITY_PATH */
 
 #ifdef CONFIG_KEYS