From mboxrd@z Thu Jan  1 00:00:00 1970
From: James Morris <jmorris@namei.org>
Subject: Re: [PATCH v2 1/5] fs: Add support for an O_MAYEXEC flag on
 sys_open()
Date: Mon, 9 Sep 2019 03:12:38 -0700 (PDT)
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To: =?ISO-8859-15?Q?Micka=EBl_Sala=FCn?= <mickael.salaun@ssi.gouv.fr>
Cc: Jeff Layton <jlayton@kernel.org>, Florian Weimer <fweimer@redhat.com>, =?ISO-8859-15?Q?Micka=EBl_Sala=FCn?= <mic@digikod.net>, linux-kernel@vger.kernel.org, Aleksa Sarai <cyphar@cyphar.com>, Alexei Starovoitov <ast@kernel.org>, Al Viro <viro@zeniv.linux.org.uk>, Andy Lutomirski <luto@kernel.org>, Christian Heimes <christian@python.org>, Daniel Borkmann <daniel@iogearbox.net>, Eric Chiang <ericchiang@google.com>, Jan Kara <jack@suse.cz>, Jann Horn <jannh@google.com>, Jonathan Corbet <corbet@lwn.net>, Kees Cook <keescook@chromium.org>, Matthew Garrett <mjg59@google.com>, Matthew Wilcox <willy@infradead.org>, Michael Kerrisk <mtk.manpages@gmail.com>, Mimi Zohar <zohar@linux.ibm.com>, =?ISO-8859-15?Q?Philippe_Tr=E9buchet?= <philippe.trebuchet@ssi.gouv.fr>, Scott Shell <scottsh@>
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On Mon, 9 Sep 2019, Mickaël Salaün 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).


-- 
James Morris
<jmorris@namei.org>

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