ext4 crypto: enforce crypto policy restrictions on cross-renames

Thanks to Chao Yu <chao2.yu@samsung.com> for pointing out the need for
this check.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/namei.c

@@ -3647,6 +3647,15 @@ static int ext4_cross_rename(struct inode *old_dir, struct dentry *old_dentry,
 	u8 new_file_type;
 	int retval;
 
+	if ((ext4_encrypted_inode(old_dir) ||
+	     ext4_encrypted_inode(new_dir)) &&
+	    (old_dir != new_dir) &&
+	    (!ext4_is_child_context_consistent_with_parent(new_dir,
+							   old.inode) ||
+	     !ext4_is_child_context_consistent_with_parent(old_dir,
+							   new.inode)))
+		return -EPERM;
+
 	dquot_initialize(old.dir);
 	dquot_initialize(new.dir);