linux-kernel - Re: [PATCH] namei: get rid of unused filename

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Date:   Wed, 1 Sep 2021 15:35:14 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Dmitry Kadashev <dkadashev@...il.com>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Christoph Hellwig <hch@...radead.org>,
        Stephen Brennan <stephen.s.brennan@...cle.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] namei: get rid of unused filename_parentat()

On Wed, Sep 01, 2021 at 03:30:56PM +0000, Al Viro wrote:
> On Wed, Sep 01, 2021 at 10:00:40PM +0700, Dmitry Kadashev wrote:
> > After the switch of kern_path_locked() to __filename_parentat() (to
> > address use after free bug) nothing is using filename_parentat(). Also,
> > filename_parentat() is inherently buggy: the "last" output arg
> > always point to freed memory.
> > 
> > Drop filename_parentat() and rename __filename_parentat() to
> > filename_parentat().
> 
> I'd rather fold that into previous patch.
> 
> And it might be better to fold filename_create() into its 2 callers
> and rename __filename_create() as well.
> 
> Let me poke around a bit...

BTW, if you look at the only caller of filename_lookup() outside of
fs/namei.c, you'll see this:
        f->refcnt++; /* filename_lookup() drops our ref. */
	ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
IOW, that thing would be better off with calling the current
__filename_lookup().

Might be better to rename filename_lookup to something different,
turn __filename_lookup() into filename_lookup() and use _that_ in
fs/fs_parser.c...