linux-kernel - Re: [patch 5/5] VFS: allow filesystem to override mknod capability checks

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Message-Id: <E1IYiH4-0001eQ-00@dorka.pomaz.szeredi.hu>
Date:	Fri, 21 Sep 2007 15:10:26 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	hch@...radead.org
CC:	miklos@...redi.hu, akpm@...ux-foundation.org, hch@...radead.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [patch 5/5] VFS: allow filesystem to override mknod capability checks

> > From: Miklos Szeredi <mszeredi@...e.cz>
> > 
> > Add a new filesystem flag, that results in the VFS not checking if the
> > current process has enough privileges to do an mknod().
> > 
> > This is needed on filesystems, where an unprivileged user may be able
> > to create a device node, without causing security problems.
> 
> A user should never be able to create devices.

A user can already create a device with fuse implicitly.  This patch
would just allow that explicitly.

Take this example: I've loopback mounted an UML disk image using fuse
(no privileges required), and want to create some device nodes.  I
can't yet boot the UML because the device node is missing from the
image.  So what should I do.  Currently I have to manipulate the
mounted image as root.  But that's really shouldn't be needed.

> And no, I don't want to see a filesystem that implements it's own
> file operations for device nodes.

I don't want that either, and it has nothing to do with this patch.

Miklos
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