Re: [PATCH for 6.19-rc1] fs: preserve file type in make_bad_inode() unless invalid

[Al Viro <viro@zeniv.linux.org.uk>]

On Wed, Dec 10, 2025 at 03:35:31PM +0000, Al Viro wrote:
> On Wed, Dec 10, 2025 at 11:09:24AM +0100, Mateusz Guzik wrote:
> > On Wed, Dec 10, 2025 at 10:45 AM Tetsuo Handa
> > <penguin-kernel@i-love.sakura.ne.jp> wrote:
> > >
> > > syzbot is hitting VFS_BUG_ON_INODE(!S_ISDIR(inode->i_mode)) check
> > > introduced by commit e631df89cd5d ("fs: speed up path lookup with cheaper
> > > handling of MAY_EXEC"), for make_bad_inode() is blindly changing file type
> > > to S_IFREG. Since make_bad_inode() might be called after an inode is fully
> > > constructed, make_bad_inode() should not needlessly change file type.
> > >
> > 
> > ouch
> > 
> > So let's say calls to make_bad_inode *after* d_instantiate are unavoidable.
> 
> ... and each one is a bug.

In this case I strongly suspect that it had been introduced in

commit 58b6fcd2ab34399258dc509f701d0986a8e0bcaa
Author: Ahmet Eray Karadag <eraykrdg1@gmail.com>
Date:   Tue Nov 18 03:18:34 2025 +0300
 
     ocfs2: mark inode bad upon validation failure during read

Folks, make_bad_inode() is *NOT* magic and having it anywhere in "hardening"
patch is a major red flag.  Please, don't do it, and I would recommend
reverting that commit, possibly along with the rest of the series.