linux-kernel - Re: [PATCH v5] hfs: update sanity check of the root record

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Message-ID: <afaca575-2393-4dd8-8159-1b79b01d007f@I-love.SAKURA.ne.jp>
Date: Tue, 16 Sep 2025 07:27:39 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: Viacheslav Dubeyko <Slava.Dubeyko@....com>,
        "glaubitz@...sik.fu-berlin.de" <glaubitz@...sik.fu-berlin.de>,
        "frank.li@...o.com" <frank.li@...o.com>,
        "slava@...eyko.com" <slava@...eyko.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Cc: "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5] hfs: update sanity check of the root record

On 2025/09/16 7:14, Viacheslav Dubeyko wrote:
> On Fri, 2025-09-12 at 23:59 +0900, Tetsuo Handa wrote:
>> syzbot is reporting that BUG() in hfs_write_inode() fires upon unmount
>> operation when the inode number of the record retrieved as a result of
>> hfs_cat_find_brec(HFS_ROOT_CNID) is not HFS_ROOT_CNID, for
>> commit b905bafdea21 ("hfs: Sanity check the root record") checked
>> the record size and the record type but did not check the inode number.
>>
>> Viacheslav Dubeyko considers that the fix should be in hfs_read_inode()
>> but Viacheslav has no time for proposing the fix [1]. Also, we can't
>> guarantee that the inode number of the record retrieved as a result of
>> hfs_cat_find_brec(HFS_ROOT_CNID) is HFS_ROOT_CNID if we validate only in
>> hfs_read_inode(). Therefore, while what Viacheslav would propose might
>> partially overwrap with my proposal, let's fix an 1000+ days old bug by
>> adding a sanity check in hfs_fill_super().
>>
> 
> I cannot accept any fix with such comment. The commit message should explain the
> issue and fix nature.

Then, see v4 at https://lkml.kernel.org/r/427fcb57-8424-4e52-9f21-7041b2c4ae5b@I-love.SAKURA.ne.jp