linux-kernel - Re: [PATCH v4] hfs: update sanity check of the root record

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Message-ID: <57d65c2f-ca35-475d-b950-8fd52b135625@I-love.SAKURA.ne.jp>
Date: Thu, 31 Jul 2025 07:02:45 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: Viacheslav Dubeyko <Slava.Dubeyko@....com>,
        "leocstone@...il.com" <leocstone@...il.com>,
        "jack@...e.cz" <jack@...e.cz>,
        "willy@...radead.org" <willy@...radead.org>,
        "brauner@...nel.org" <brauner@...nel.org>
Cc: "glaubitz@...sik.fu-berlin.de" <glaubitz@...sik.fu-berlin.de>,
        "frank.li@...o.com" <frank.li@...o.com>,
        "slava@...eyko.com" <slava@...eyko.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH v4] hfs: update sanity check of the root record

On 2025/07/31 4:24, Viacheslav Dubeyko wrote:
> If we considering case HFS_CDR_DIR in hfs_read_inode(), then we know that it
> could be HFS_POR_CNID, HFS_ROOT_CNID, or >= HFS_FIRSTUSER_CNID. Do you mean that
> HFS_POR_CNID could be a problem in hfs_write_inode()?

Yes. Passing one of 1, 5 or 15 instead of 2 from hfs_fill_super() triggers BUG()
in hfs_write_inode(). We *MUST* validate at hfs_fill_super(), or hfs_read_inode()
shall have to also reject 1, 5 and 15 (and as a result only accept 2).