linux-kernel - Re: [patch 07/10] unprivileged mounts: add sysctl tunable for "safe" property

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Message-ID: <20080122204828.GA1212@sergelap.austin.ibm.com>
Date:	Tue, 22 Jan 2008 14:48:28 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	serue@...ibm.com, akpm@...ux-foundation.org, hch@...radead.org,
	viro@....linux.org.uk, kzak@...hat.com,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	containers@...ts.osdl.org, util-linux-ng@...r.kernel.org
Subject: Re: [patch 07/10] unprivileged mounts: add sysctl tunable for
	"safe" property

Quoting Miklos Szeredi (miklos@...redi.hu):
> > What do you think about doing this only if FS_SAFE is also set,
> > so for instance at first only FUSE would allow itself to be
> > made user-mountable?
> > 
> > A safe thing to do, or overly intrusive?
> 
> It goes somewhat against the "no policy in kernel" policy ;).  I think
> the warning in the documentation should be enough to make sysadmins
> think twice before doing anything foolish:

Warning in which documentation?  A sysadmin considering setting fs_safe
for ext2 or xfs isn't going to be looking at fuse docs, which I think is
what you're talking about.  Are you going to add a file under
Documentation/filesystems?

> > +Care should be taken when enabling this, since most
> > +filesystems haven't been designed with unprivileged mounting
> > +in mind.
> > +
> 
> BTW, filesystems like 'proc' and 'sysfs' should also be safe, although
> the only use for them being marked safe is if the users are allowed to
> umount them from their private namespace (otherwise a 'mount --bind'
> has the same effect as a new mount).
> 
> Thanks,
> Miklos
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