Re: [PATCH v7 0/7] Add support for O_MAYEXEC

From: "Mickaël Salaün" <mic@digikod.net>
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>,
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	"Christian Brauner" <christian.brauner@ubuntu.com>,
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	"Deven Bowers" <deven.desai@linux.microsoft.com>,
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Subject: Re: [PATCH v7 0/7] Add support for O_MAYEXEC
Date: Tue, 11 Aug 2020 10:50:53 +0200	[thread overview]
Message-ID: <c0224c08-f669-168e-3bb4-35eceec96a8b@digikod.net> (raw)
In-Reply-To: <26a4a8378f3b4ad28eaa476853092716@AcuMS.aculab.com>

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/