Re: [PATCH v2 1/5] fs: Add support for an O_MAYEXEC flag on sys_open()

From: MickaÃl SalaÃn
Date: Mon Sep 09 2019 - 06:54:22 EST

On 09/09/2019 12:12, James Morris wrote:
> On Mon, 9 Sep 2019, MickaÃl SalaÃn wrote:
>> On 06/09/2019 21:03, James Morris wrote:
>>> On Fri, 6 Sep 2019, Jeff Layton wrote:
>>>> The fact that open and openat didn't vet unknown flags is really a bug.
>>>> Too late to fix it now, of course, and as Aleksa points out, we've
>>>> worked around that in the past. Now though, we have a new openat2
>>>> syscall on the horizon. There's little need to continue these sorts of
>>>> hacks.
>>>> New open flags really have no place in the old syscalls, IMO.
>>> Agree here. It's unfortunate but a reality and Linus will reject any such
>>> changes which break existing userspace.
>> Do you mean that adding new flags to open(2) is not possible?
>> Does it means that unspecified behaviors are definitely part of the
>> Linux specification and can't be fixed?
> This is my understanding.
>> As I said, O_MAYEXEC should be ignored if it is not supported by the
>> kernel, which perfectly fit with the current open(2) flags behavior, and
>> should also behave the same with openat2(2).
> The problem here is programs which are already using the value of
> O_MAYEXEC, which will break. Hence, openat2(2).

Well, it still depends on the sysctl, which doesn't enforce anything by
default, hence doesn't break existing behavior, and this unused flags
could be fixed/removed or reported by sysadmins or distro developers.

MickaÃl SalaÃn

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