Message-ID: <53A00EDB.3050108@redhat.com>
Date: Tue, 17 Jun 2014 11:48:11 +0200
From: Florian Weimer <fweimer@redhat.com>
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To: Andy Lutomirski <luto@amacapital.net>, "Theodore Ts'o" <tytso@mit.edu>,
        David Herrmann <dh.herrmann@gmail.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Hugh Dickins <hughd@google.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Karol Lewandowski <k.lewandowsk@samsung.com>,
        Kay Sievers <kay@vrfy.org>, Daniel Mack <zonque@gmail.com>,
        Lennart Poettering <lennart@poettering.net>,
        John Stultz <john.stultz@linaro.org>,
        Greg Kroah-Hartman <greg@kroah.com>, Tejun Heo <tj@kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ryan Lortie <desrt@desrt.ca>,
        "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Subject: Re: [PATCH 0/6] File Sealing & memfd_create()
References: <1395256011-2423-1-git-send-email-dh.herrmann@gmail.com> <20140320153250.GC20618@thunk.org> <CANq1E4SUXrzAV8FS8HVYxnRVb1oOR6HSTyucJzyFs5PuS5Y88A@mail.gmail.com> <20140320163806.GA10440@thunk.org> <5346ED93.9040500@amacapital.net> <20140410203246.GB31614@thunk.org> <CALCETrVmaGNCxo-L4-dPbUev3VXXEPR7xBzo3Fux6ny7yh_Gzw@mail.gmail.com>
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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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