Re: [PATCH] [RFC] fs: Possible filp_open race experiment

[Christoph Hellwig]

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.