From: ebiederm@xmission.com (Eric W. Biederman)
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: serue@us.ibm.com, akpm@linux-foundation.org, hch@infradead.org,
viro@ZenIV.linux.org.uk, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: unprivileged mounts git tree
Date: Thu, 11 Sep 2008 12:04:41 -0700 [thread overview]
Message-ID: <m17i9icxme.fsf@frodo.ebiederm.org> (raw)
In-Reply-To: <E1KdnOb-00068L-Eq@pomaz-ex.szeredi.hu> (Miklos Szeredi's message of "Thu, 11 Sep 2008 16:43:45 +0200")
Miklos Szeredi <miklos@szeredi.hu> writes:
> On Thu, 11 Sep 2008, ebiederm@xmission.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?
I don't think only user mounts is the right filter.
We have support for lazy unmounts so it is possible to handle
that case.
Technically all we need to do is transform d_mounted from a counter
to a hlist_head and thread yet another list through struct vfs_mount
to track this.
I need to think about the semantics a little more before I have a good
feel of what makes sense. In particular do we want a full
recursive lazy unmount or do we want to handle submounts in a different
way.
This also intersects in interesting ways with dcache pruning, and
automounting.
Eric
next prev parent reply other threads:[~2008-09-11 19:15 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-07 12:05 unprivileged mounts git tree Miklos Szeredi
2008-08-07 22:27 ` Serge E. Hallyn
2008-08-08 0:07 ` Eric W. Biederman
2008-08-08 0:25 ` Serge E. Hallyn
2008-08-25 11:01 ` Miklos Szeredi
2008-08-27 15:36 ` Serge E. Hallyn
2008-08-27 15:55 ` Miklos Szeredi
2008-08-27 18:46 ` Serge E. Hallyn
2008-09-03 18:45 ` Miklos Szeredi
2008-09-03 21:54 ` Serge E. Hallyn
2008-09-03 22:02 ` Serge E. Hallyn
2008-09-03 22:25 ` Miklos Szeredi
2008-09-03 22:43 ` Serge E. Hallyn
2008-09-04 6:42 ` Miklos Szeredi
2008-09-04 13:28 ` Serge E. Hallyn
2008-09-04 14:06 ` Miklos Szeredi
2008-09-04 15:40 ` Miklos Szeredi
2008-09-04 16:17 ` Serge E. Hallyn
2008-09-04 17:42 ` Miklos Szeredi
2008-09-04 17:48 ` Serge E. Hallyn
2008-09-04 18:03 ` Miklos Szeredi
2008-09-04 18:49 ` Serge E. Hallyn
2008-09-04 22:26 ` Miklos Szeredi
2008-09-04 23:32 ` Serge E. Hallyn
2008-09-05 15:31 ` Serge E. Hallyn
2008-09-09 13:34 ` Miklos Szeredi
2008-09-11 10:37 ` Eric W. Biederman
2008-09-11 14:43 ` Miklos Szeredi
2008-09-11 15:20 ` Serge E. Hallyn
2008-09-11 15:44 ` Miklos Szeredi
2008-09-11 18:54 ` Eric W. Biederman
2008-09-12 22:08 ` Serge E. Hallyn
2008-09-13 3:12 ` Eric W. Biederman
2008-09-14 1:56 ` Serge E. Hallyn
2008-09-14 3:06 ` Eric W. Biederman
2008-09-30 19:39 ` Serge E. Hallyn
2008-10-06 11:05 ` Miklos Szeredi
2008-09-11 19:04 ` Eric W. Biederman [this message]
2008-09-11 19:58 ` Eric W. Biederman
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