linux-kernel - Re: [PATCH] vfs: new O

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Date:	Mon, 28 Sep 2009 15:10:25 +0100
From:	Jamie Lokier <jamie@...reable.org>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	Valdis.Kletnieks@...edu, linux@...blig.org, agruen@...e.de,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfs: new O_NODE open flag

Miklos Szeredi wrote:
> > Hmm.  I have just tried, and you _can _use open("/proc/self/fd/%d",
> > O_RDWR) to re-open with more permissions when you can't access the
> > path which /proc/self/fd/%d pretends to link to.  It looks a bit
> > dubious, as you might have been passed an O_RDONLY descriptor with the
> > intention that you can't write to it...  Oh well!
> 
> True, /proc gives you access to the underlying "path" of an open file
> descriptor.  If you don't want that, don't mount /proc in your limited
> namespace.

I wasn't using a limited namespace.

Just a directory without permission to be searched, and as a regular
user - which is historically supposed to prevent you from opening
files in it.

-- Jamie
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