linux-kernel - RE: [PATCH v7 0/7] Add support for O

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Message-ID: <26a4a8378f3b4ad28eaa476853092716@AcuMS.aculab.com>
Date:   Tue, 11 Aug 2020 08:09:10 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Mickaël Salaün' <mic@...ikod.net>,
        Al Viro <viro@...iv.linux.org.uk>
CC:     Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Aleksa Sarai <cyphar@...har.com>,
        "Alexei Starovoitov" <ast@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        "Christian Brauner" <christian.brauner@...ntu.com>,
        Christian Heimes <christian@...hon.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Deven Bowers <deven.desai@...ux.microsoft.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "Eric Biggers" <ebiggers@...nel.org>,
        Eric Chiang <ericchiang@...gle.com>,
        "Florian Weimer" <fweimer@...hat.com>,
        James Morris <jmorris@...ei.org>, Jan Kara <jack@...e.cz>,
        Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>,
        Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
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        Mimi Zohar <zohar@...ux.ibm.com>,
        Philippe Trébuchet 
        <philippe.trebuchet@....gouv.fr>,
        "Scott Shell" <scottsh@...rosoft.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Shuah Khan <shuah@...nel.org>,
        Steve Dower <steve.dower@...hon.org>,
        Steve Grubb <sgrubb@...hat.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Thibaut Sautereau <thibaut.sautereau@...p-os.org>,
        Vincent Strubel <vincent.strubel@....gouv.fr>,
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        <kernel-hardening@...ts.openwall.com>,
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        <linux-security-module@...r.kernel.org>,
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Subject: RE: [PATCH v7 0/7] Add support for O_MAYEXEC

> On 11/08/2020 00:28, Al Viro wrote:
> > On Mon, Aug 10, 2020 at 10:09:09PM +0000, David Laight wrote:
> >>> On Mon, Aug 10, 2020 at 10:11:53PM +0200, Mickaël Salaün wrote:
> >>>> It seems that there is no more complains nor questions. Do you want me
> >>>> to send another series to fix the order of the S-o-b in patch 7?
> >>>
> >>> There is a major question regarding the API design and the choice of
> >>> hooking that stuff on open().  And I have not heard anything resembling
> >>> a coherent answer.
> >>
> >> To me O_MAYEXEC is just the wrong name.
> >> The bit would be (something like) O_INTERPRET to indicate
> >> what you want to do with the contents.
> 
> The properties is "execute permission". This can then be checked by
> interpreters or other applications, then the generic O_MAYEXEC name.

The english sense of MAYEXEC is just wrong for what you are trying
to check.

> > ... which does not answer the question - name of constant is the least of
> > the worries here.  Why the hell is "apply some unspecified checks to
> > file" combined with opening it, rather than being an independent primitive
> > you apply to an already opened file?  Just in case - "'cuz that's how we'd
> > done it" does not make a good answer...

Maybe an access_ok() that acts on an open fd would be more
appropriate.
Which might end up being an fcntrl() action.
That would give you a full 32bit mask of options.

	David

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