linux-kernel - Re: [PATCH] add new prctl for a per process wide close on exec

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Message-ID: <20131022194836.GZ13318@ZenIV.linux.org.uk>
Date:	Tue, 22 Oct 2013 20:48:37 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Stefani Seibold <stefani@...bold.net>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	akpm@...ux-foundation.org, mingo@...hat.com, peterz@...radead.org
Subject: Re: [PATCH] add new prctl for a per process wide close on exec

On Tue, Oct 22, 2013 at 09:27:18PM +0200, Stefani Seibold wrote:

> This patch will increase security since no developers can review all libraries
> which there are using. Also in a team of developers it is not always possible
> to have a full survey over the code which is produced. Or the output of a code
> generators and so one. This patch allows a kind of preventive measures.
> 
> It can also prevent resource occupation. Imagine a long running process (a
> daemon) is execute from the application after open some file desciptors. For
> example libpcsclite.so will not open the socket with SOCK_CLOEXEC. Or a device
> driver which alows only a single open. In both cases the resource cannot
> reopened after a close. Sigh!
> 
> What do you think?

That it's a bad idea.  Not to mention anything else, the same unreviewed
libraries can get buggered if the program sets that "global close-on-exec"
and it's not at all obvious whether the breakage from that change will be less
or more dangerous than leaking opened files to children.

Al, fully expecting the Linux S-M crowd to jump on that one and come up with
yet another one-shot LSM... ;-/
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