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Subject: Re: [PATCH v7 0/7] Add support for O_MAYEXEC
To:     David Laight <David.Laight@aculab.com>,
        Al Viro <viro@zeniv.linux.org.uk>
Cc:     Kees Cook <keescook@chromium.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Aleksa Sarai <cyphar@cyphar.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Christian Heimes <christian@python.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Deven Bowers <deven.desai@linux.microsoft.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Eric Biggers <ebiggers@kernel.org>,
        Eric Chiang <ericchiang@google.com>,
        Florian Weimer <fweimer@redhat.com>,
        James Morris <jmorris@namei.org>, Jan Kara <jack@suse.cz>,
        Jann Horn <jannh@google.com>, Jonathan Corbet <corbet@lwn.net>,
        Lakshmi Ramasubramanian <nramas@linux.microsoft.com>,
        Matthew Garrett <mjg59@google.com>,
        Matthew Wilcox <willy@infradead.org>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Mimi Zohar <zohar@linux.ibm.com>,
        =?UTF-8?Q?Philippe_Tr=c3=a9buchet?= 
        <philippe.trebuchet@ssi.gouv.fr>,
        Scott Shell <scottsh@microsoft.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Shuah Khan <shuah@kernel.org>,
        Steve Dower <steve.dower@python.org>,
        Steve Grubb <sgrubb@redhat.com>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Thibaut Sautereau <thibaut.sautereau@clip-os.org>,
        Vincent Strubel <vincent.strubel@ssi.gouv.fr>,
        "kernel-hardening@lists.openwall.com" 
        <kernel-hardening@lists.openwall.com>,
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        <linux-security-module@vger.kernel.org>,
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From:   =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= <mic@digikod.net>
Message-ID: <c0224c08-f669-168e-3bb4-35eceec96a8b@digikod.net>
Date:   Tue, 11 Aug 2020 10:50:53 +0200
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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.net/