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From: "Serge E. Hallyn" <serue@us.ibm.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: serue@us.ibm.com, akpm@linux-foundation.org, hch@infradead.org,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [patch 07/10] unprivileged mounts: add sysctl tunable for "safe" property
Date: Wed, 6 Feb 2008 16:45:27 -0600	[thread overview]
Message-ID: <20080206224527.GB24246@sergelap.austin.ibm.com> (raw)
In-Reply-To: <E1JMrXw-0000qq-O9@pomaz-ex.szeredi.hu>

Quoting Miklos Szeredi (miklos@szeredi.hu):
> > > +	t->table[0].mode = 0644;
> > 
> > Yikes, this could be a problem for containers, as it's simply tied to
> > uid 0, whereas tying it to a capability would let us solve it with
> > capability bounds.
> > 
> > This might mean more urgency to get user namespaces working at least
> > with sysfs, else this is a quick way around having CAP_SYS_ADMIN taken
> > out of a container's capability bounding set.
> 
> I think I understand the problem, but not the solution.  How do user
> namespaces going to help?

Well it somewhat depends on how we implement userns for filesystems
in the first place, and whether we end up splitting sysfs into
sub-filesystems as I think Eric Biederman has been advocating.  My
thoughts had been running along the lines of just tagging vfsmounts
with userns of the mounting process.  A task from outside the mounting
process' namespace would get user other permissions whether or not
its uid was the owning uid or uid 0 (unless the task had CAP_NS_OVERRIDE).

But really it gets more complicated for sysfs than something like ext2
since we really want to be able to filter files and directories for
different namespaces...  Handling sysfs user namespaces before we sort
out the rest of the sysfs stuff (being hashed out with network
namespaces) seems like jumping the gun a bit.

> Maybe sysctls just need to check capabilities, instead of uids.  I
> think that would make a lot of sense anyway.

Would it be as simple as tagging the inodes with capability sets?  One
set for writing, or one each for reading and writing?

thanks,
-serge

  reply	other threads:[~2008-02-06 22:45 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-05 21:36 [patch 00/10] mount ownership and unprivileged mount syscall (v8) Miklos Szeredi
2008-02-05 21:36 ` [patch 01/10] unprivileged mounts: add user mounts to the kernel Miklos Szeredi
2008-02-05 21:36 ` [patch 02/10] unprivileged mounts: allow unprivileged umount Miklos Szeredi
2008-02-05 21:36 ` [patch 03/10] unprivileged mounts: propagate error values from clone_mnt Miklos Szeredi
2008-02-05 21:36 ` [patch 04/10] unprivileged mounts: account user mounts Miklos Szeredi
2008-02-05 21:36 ` [patch 05/10] unprivileged mounts: allow unprivileged bind mounts Miklos Szeredi
2008-02-05 21:36 ` [patch 06/10] unprivileged mounts: allow unprivileged mounts Miklos Szeredi
2008-02-05 21:36 ` [patch 07/10] unprivileged mounts: add sysctl tunable for "safe" property Miklos Szeredi
2008-02-06 20:21   ` Serge E. Hallyn
2008-02-06 21:11     ` Miklos Szeredi
2008-02-06 22:45       ` Serge E. Hallyn [this message]
2008-02-07  8:09         ` Miklos Szeredi
2008-02-07 14:05           ` Serge E. Hallyn
2008-02-07 14:36             ` Miklos Szeredi
2008-02-07 16:57               ` Serge E. Hallyn
2008-02-07 15:33   ` Aneesh Kumar K.V
2008-02-07 16:24     ` Miklos Szeredi
2008-02-05 21:36 ` [patch 08/10] unprivileged mounts: make fuse safe Miklos Szeredi
2008-02-05 21:36 ` [patch 09/10] unprivileged mounts: propagation: inherit owner from parent Miklos Szeredi
2008-02-05 21:36 ` [patch 10/10] unprivileged mounts: add "no submounts" flag Miklos Szeredi
2008-02-15  6:21 ` [patch 00/10] mount ownership and unprivileged mount syscall (v8) Andrew Morton
2008-02-15  9:01   ` Christoph Hellwig
2008-02-15  9:09     ` Andrew Morton
2008-02-15  9:14       ` Christoph Hellwig
2008-02-18 11:47         ` Miklos Szeredi
2008-02-23 16:09           ` Al Viro
2008-02-23 17:33             ` Miklos Szeredi
2008-02-23 18:57               ` Al Viro
2008-02-23 19:48                 ` Miklos Szeredi
  -- strict thread matches above, loose matches on Subject: below --
2008-01-16 12:31 [patch 00/10] mount ownership and unprivileged mount syscall (v7) Miklos Szeredi
2008-01-16 12:31 ` [patch 07/10] unprivileged mounts: add sysctl tunable for "safe" property Miklos Szeredi
2008-01-21 20:32   ` Serge E. Hallyn
2008-01-21 21:37     ` Miklos Szeredi
2008-01-22 20:48       ` Serge E. Hallyn
2008-01-22 22:59         ` Miklos Szeredi
2008-01-23  0:00           ` Serge E. Hallyn

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