f2fs: fix potential corruption when moving a directory

F2FS has the same issue in ext4_rename causing crash revealed by
xfstests/generic/707.

See also commit 0813299 ("ext4: Fix possible corruption when moving a directory")

CC: stable@vger.kernel.org
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/namei.c

@@ -995,12 +995,20 @@ static int f2fs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
 			goto out;
 	}
 
+	/*
+	 * Copied from ext4_rename: we need to protect against old.inode
+	 * directory getting converted from inline directory format into
+	 * a normal one.
+	 */
+	if (S_ISDIR(old_inode->i_mode))
+		inode_lock_nested(old_inode, I_MUTEX_NONDIR2);
+
 	err = -ENOENT;
 	old_entry = f2fs_find_entry(old_dir, &old_dentry->d_name, &old_page);
 	if (!old_entry) {
 		if (IS_ERR(old_page))
 			err = PTR_ERR(old_page);
-		goto out;
+		goto out_unlock_old;
 	}
 
 	if (S_ISDIR(old_inode->i_mode)) {
@@ -1108,6 +1116,9 @@ static int f2fs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
 
 	f2fs_unlock_op(sbi);
 
+	if (S_ISDIR(old_inode->i_mode))
+		inode_unlock(old_inode);
+
 	if (IS_DIRSYNC(old_dir) || IS_DIRSYNC(new_dir))
 		f2fs_sync_fs(sbi->sb, 1);
 
@@ -1122,6 +1133,9 @@ static int f2fs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
 		f2fs_put_page(old_dir_page, 0);
 out_old:
 	f2fs_put_page(old_page, 0);
+out_unlock_old:
+	if (S_ISDIR(old_inode->i_mode))
+		inode_unlock(old_inode);
 out:
 	iput(whiteout);
 	return err;