ubifs: Rectify space budget for ubifs_xrename()

[ Upstream commit 1b2ba09 ]

There is no space budget for ubifs_xrename(). It may let
make_reservation() return with -ENOSPC, which could turn
ubifs to read-only mode in do_writepage() process.
Fix it by adding space budget for ubifs_xrename().

Fetch a reproducer in [Link].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216569
Fixes: 9ec6496 ("ubifs: Implement RENAME_EXCHANGE")
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>

fs/ubifs/dir.c

@@ -1538,6 +1538,10 @@ static int ubifs_xrename(struct inode *old_dir, struct dentry *old_dentry,
  return err;
  }
 
+ err = ubifs_budget_space(c, &req);
+ if (err)
+ goto out;
+
  lock_4_inodes(old_dir, new_dir, NULL, NULL);
 
  time = current_time(old_dir);
@@ -1563,6 +1567,7 @@ static int ubifs_xrename(struct inode *old_dir, struct dentry *old_dentry,
  unlock_4_inodes(old_dir, new_dir, NULL, NULL);
  ubifs_release_budget(c, &req);
 
+out:
  fscrypt_free_filename(&fst_nm);
  fscrypt_free_filename(&snd_nm);
  return err;