linux-kernel - Re: [PATCH] autofs4 - detect invalid direct mount requests

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Message-Id: <1215006402.3046.72.camel@raven.themaw.net>
Date:	Wed, 02 Jul 2008 21:46:41 +0800
From:	Ian Kent <raven@...maw.net>
To:	Jeff Moyer <jmoyer@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	autofs mailing list <autofs@...ux.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] autofs4 - detect invalid direct mount requests


On Fri, 2008-06-20 at 09:00 -0400, Jeff Moyer wrote:
> Ian Kent <raven@...maw.net> writes:
> 
> > autofs v5 dierct and offset mounts within an autofs filesystem are
> > triggered by existing autofs triger mounts so the mount point dentry
> > must be positive. If the mount point dentry is negative then the
> > trigger doesn't exist so we can return fail immediately.
> 
> What are the conditions that lead us here in that case?

A multi-mount that has no root mount gets a lookup for an offset that
doesn't exist (ie. the trigger hasn't been mounted). Then ->lookup()
will create a negative dentry and send a mount request to the daemon. It
is a bit of a special case but it helps a little.

Ian


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