linux-kernel - Re: [PATCH 0/6] File Sealing & memfd

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Date:	Tue, 17 Jun 2014 11:48:11 +0200
From:	Florian Weimer <fweimer@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>,
	"Theodore Ts'o" <tytso@....edu>,
	David Herrmann <dh.herrmann@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Hugh Dickins <hughd@...gle.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Karol Lewandowski <k.lewandowsk@...sung.com>,
	Kay Sievers <kay@...y.org>, Daniel Mack <zonque@...il.com>,
	Lennart Poettering <lennart@...ttering.net>,
	John Stultz <john.stultz@...aro.org>,
	Greg Kroah-Hartman <greg@...ah.com>, Tejun Heo <tj@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ryan Lortie <desrt@...rt.ca>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
Subject: Re: [PATCH 0/6] File Sealing & memfd_create()

On 04/10/2014 10:37 PM, Andy Lutomirski wrote:

> It occurs to me that, before going nuts with these kinds of flags, it
> may pay to just try to fix the /proc/self/fd issue for real -- we
> could just make open("/proc/self/fd/3", O_RDWR) fail if fd 3 is
> read-only.  That may be enough for the file sealing thing.

Increasing privilege on O_PATH descriptors via access through 
/proc/self/fd is part of the userspace API.  The same thing might be 
true for O_RDONLY descriptors, but it's a bit less likely that there are 
any users out there.  In any case, I'm not sure it makes sense to plug 
the O_RDONLY hole while leaving the O_PATH hole open.

-- 
Florian Weimer / Red Hat Product Security Team
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