linux-kernel - Re: [PATCH] [RFC] fs: Possible filp

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Date:   Tue, 31 Jan 2017 14:17:59 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Marek Vasut <marex@...x.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
        Joel Becker <jlbec@...lplan.org>
Subject: Re: [PATCH] [RFC] fs: Possible filp_open race experiment

On Tue, Jan 31, 2017 at 01:58:14PM +0100, Christoph Hellwig wrote:
> On Tue, Jan 31, 2017 at 11:21:02AM +0100, Greg Kroah-Hartman wrote:
> > 
> > -next isn't Linus's tree, sometimes stuff sits in there for years :)
> > 
> > Anyway, if this is a configfs issue, Christoph and Joel can take a look
> > at it.  Any reason you didn't cc: Joel as well (the MAINTAINERS file is
> > your friend...)
> 
> It's really a mismatched assumption.  The configfs binary file
> code just chunks updates up into a buffer, which only gets flushed
> at ->release time.  If we'd move that to ->flush the issue Marek reports
> would be fixed.
> 
> But I don't think we want that - triggering a filp_open from the update
> of a _binary_ attribute for a start is wrong.  And second doing this
> using ->fs of a random calling process is bound to cause problems.
> 
> I think he is using the wrong kind of interface for the job.

Ah, that's why no one has seen this before :)

So, the DT overlay code needs to be fixed...

thanks,

greg k-h