linux-kernel - Re: [PATCH 4/4] autofs4 - add miscelaneous device for ioctls

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Date:	Thu, 7 Aug 2008 23:33:25 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ian Kent <raven@...maw.net>
Cc:	autofs@...ux.kernel.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 4/4] autofs4 - add miscelaneous device for ioctls

On Fri, 08 Aug 2008 14:12:21 +0800 Ian Kent <raven@...maw.net> wrote:

> > > No problem.
> > > You mentioned this last time as well.
> > > 
> > > Since there are a couple of possible approaches and I wasn't sure which
> > > way to go I thought I'd post it as is and get feedback then make it a
> > > followup patch.
> > > 
> > > Could the pthreads user space daemon exec something between fd_install()
> > > and set_close_on_exec()? 
> > 
> > Gee, I don't know, it would depend on the context.
> > 
> > Is that a private file*?  Was it just created, and is there no
> > possibility that any other thread can be sharing it anyway?  If so,
> > there's no problem.
> 
> The problem is that autofs threads can exec mount or umount at any time
> and we see annoying selinux file descriptor leak security violation
> messages. So the point of this is to set the bit at the same time as the
> file is inserted into the table.
> 
> > 
> > > Perhaps there are some other alternative approaches to this.
> > > 
> > > Suggestions?
> > 
> > I don't know enough about autofs nor about what problem you're
> > attacking here to be able to say, sorry.  I don't even know why
> > close_on_exec is being set?
> 
> OK, sorry.
> 
> What I'm really after is:
> Should I do this at all, given the above?

I don't reliably know, sorry.  <does viro summoning dance>

> If this is sensible, should a parameter be added to fd_insall() to allow
> it to be requested at descriptor install or should a new function, say,
> fd_install_close_on_exec() be added?

If we decide to do it this way, then we can add an extra arg to
fd_install(), I guess.

void fd_install(unsigned int fd, struct file *file,
		void (*callback)(struct file *));

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