linux-kernel - Re: [PATCH v3 4/6] blktrace: fix debugfs use after free

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Message-ID: <20200429125726.GA2123334@kroah.com>
Date:   Wed, 29 Apr 2020 14:57:26 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     Christoph Hellwig <hch@...radead.org>, axboe@...nel.dk,
        viro@...iv.linux.org.uk, bvanassche@....org, rostedt@...dmis.org,
        mingo@...hat.com, jack@...e.cz, ming.lei@...hat.com,
        nstange@...e.de, akpm@...ux-foundation.org, mhocko@...e.com,
        yukuai3@...wei.com, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Omar Sandoval <osandov@...com>,
        Hannes Reinecke <hare@...e.com>,
        Michal Hocko <mhocko@...nel.org>,
        syzbot+603294af2d01acfdd6da@...kaller.appspotmail.com
Subject: Re: [PATCH v3 4/6] blktrace: fix debugfs use after free

On Wed, Apr 29, 2020 at 12:21:52PM +0000, Luis Chamberlain wrote:
> On Wed, Apr 29, 2020 at 05:04:06AM -0700, Christoph Hellwig wrote:
> > On Wed, Apr 29, 2020 at 12:02:30PM +0000, Luis Chamberlain wrote:
> > > > Err, that function is static and has two callers.
> > > 
> > > Yes but that is to make it easier to look for who is creating the
> > > debugfs_dir for either the request_queue or partition. I'll export
> > > blk_debugfs_root and we'll open code all this.
> > 
> > No, please not.  exported variables are usually a bad idea.  Just
> > skip the somewhat pointless trivial static function.
> 
> Alrighty. It has me thinking we might want to only export those symbols
> to a specific namespace. Thoughts, preferences?
> 
> BLOCK_GENHD_PRIVATE ?

That's a nice add-on issue after this is fixed.  As Christoph and I
pointed out, you have _less_ code in the file if you remove the static
wrapper function.  Do that now and then worry about symbol namespaces
please.

thanks,

greg k-h