linux-kernel - Re: unprivileged mounts git tree

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Message-Id: <E1KdnOb-00068L-Eq@pomaz-ex.szeredi.hu>
Date:	Thu, 11 Sep 2008 16:43:45 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	ebiederm@...ssion.com
CC:	miklos@...redi.hu, serue@...ibm.com, akpm@...ux-foundation.org,
	hch@...radead.org, viro@...IV.linux.org.uk,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: unprivileged mounts git tree

On Thu, 11 Sep 2008, ebiederm@...ssion.com (Eric W. Biederman)
> There is a weird corner case I'm trying to wrap my head around.
> unlink and rmdir do not work on dentries that are mount points
> in another mount namespace.
> 
> Which is at least needed for the moment so we don't leak mounts.
> 
> Once we have unprivileged mounts does that introduce a DOS attack?

Hmm, yes.  That's a tough one...

I think if the dentry has only user mounts, unlink should go ahead and
on success dissolve any mounts on the dentry.  Does that sound
workable?

Thanks,
Miklos
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