On Mon, 9 Sep 2019, Mickaël Salaün wrote:

On 06/09/2019 21:03, James Morris wrote:

quoted

On Fri, 6 Sep 2019, Jeff Layton wrote:

quoted

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
[off-list ref]