linux-kernel - Re: [patch 2/2] VFS: allow filesystem to override mknod capability checks

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Message-ID: <20070924123813.GB17409@infradead.org>
Date:	Mon, 24 Sep 2007 13:38:13 +0100
From:	Christoph Hellwig <hch@...radead.org>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	hch@...radead.org, trond.myklebust@....uio.no,
	adilger@...sterfs.com, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [patch 2/2] VFS: allow filesystem to override mknod capability checks

On Mon, Sep 24, 2007 at 02:25:54PM +0200, Miklos Szeredi wrote:
> From: Miklos Szeredi <mszeredi@...e.cz>
> 
> Add a new super block flag, that results in the VFS not checking if
> the current process has enough privileges to do an mknod().
> 
> If this flag is set, all mounts for this super block will have the
> "nodev" flag implied.
> 
> This is needed on filesystems, where an unprivileged user may be able
> to create a device node, without causing security problems.
> 
> One such example is "mountlo" a loopback mount utility implemented
> with fuse and UML, which runs as an unprivileged userspace process.
> In this case the user does in fact have the right to create device
> nodes within the filesystem image, as long as the user has write
> access to the image.  Since the filesystem is mounted with "nodev",
> adding device nodes is not a security concern.

This one looks okay, but I'd prefer to not put it in until we actually
have proper non-privilegued mounts.

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