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Date: Tue, 11 Aug 2020 09:07:41 -0400
From: Steve Grubb <sgrubb@...hat.com>
To: David Laight <David.Laight@...lab.com>, Al Viro <viro@...iv.linux.org.uk>, Mickaël Salaün <mic@...ikod.net>
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>, Matthew Garrett <mjg59@...gle.com>, Matthew Wilcox <willy@...radead.org>, Michael Kerrisk <mtk.manpages@...il.com>, Mimi Zohar <zohar@...ux.ibm.com>, Philippe Trébuchet <philippe.trebuchet@....gouv.fr>, Scott Shell <scottsh@mi
crosoft.com>, Sean Christopherson <sean.j.christopherson@...el.com>, Shuah Khan <shuah@...nel.org>, Steve Dower <steve.dower@...hon.org>, Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>, Thibaut Sautereau <thibaut.sautereau@...p-os.org>, Vincent Strubel <vincent.strubel@....gouv.fr>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>, "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>, "linux-security-module@...r.kernel.org" <linux-security-module@...r.kernel.org>, "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH v7 0/7] Add support for O_MAYEXEC
On Tuesday, August 11, 2020 4:50:53 AM EDT Mickaël Salaün wrote:
> On 11/08/2020 10:09, David Laight wrote:
> >> 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.
>
> We think it reflects exactly what it's purpose is.
>
> >>> ... 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.
>
> I previously talk about fcntl(2):
> https://lore.kernel.org/lkml/eaf5bc42-e086-740b-a90c-93e67c535eee@digikod.n
> et/
Fcntl is too late for anything using FANOTIFY. Everything needs to be upfront
or other security systems cannot use it.
-Steve
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