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Date: Thu, 30 Apr 2020 11:54:29 +1000
From: Aleksa Sarai <>
To: Mickaël Salaün <>
Cc:, Alexei Starovoitov <>,
	Al Viro <>,
	Andy Lutomirski <>,
	Christian Heimes <>,
	Daniel Borkmann <>,
	Deven Bowers <>,
	Eric Chiang <>,
	Florian Weimer <>,
	James Morris <>, Jan Kara <>,
	Jann Horn <>, Jonathan Corbet <>,
	Kees Cook <>,
	Matthew Garrett <>,
	Matthew Wilcox <>,
	Michael Kerrisk <>,
	Mickaël Salaün <>,
	Mimi Zohar <>,
	Philippe Trébuchet <>,
	Scott Shell <>,
	Sean Christopherson <>,
	Shuah Khan <>, Steve Dower <>,
	Steve Grubb <>,
	Thibaut Sautereau <>,
	Vincent Strubel <>,,,,
Subject: Re: [PATCH v3 0/5] Add support for RESOLVE_MAYEXEC

On 2020-04-28, Mickaël Salaün <> wrote:
> The goal of this patch series is to enable to control script execution
> with interpreters help.  A new RESOLVE_MAYEXEC flag, usable through
> openat2(2), is added to enable userspace script interpreter to delegate
> to the kernel (and thus the system security policy) the permission to
> interpret/execute scripts or other files containing what can be seen as
> commands.
> This third patch series mainly differ from the previous one by relying
> on the new openat2(2) system call to get rid of the undefined behavior
> of the open(2) flags.  Thus, the previous O_MAYEXEC flag is now replaced
> with the new RESOLVE_MAYEXEC flag and benefits from the openat2(2)
> strict check of this kind of flags.

My only strong upfront objection is with this being a RESOLVE_ flag.

RESOLVE_ flags have a specific meaning (they generally apply to all
components, and affect the rules of path resolution). RESOLVE_MAYEXEC
does neither of these things and so seems out of place among the other
RESOLVE_ flags.

I would argue this should be an O_ flag, but not supported for the
old-style open(2). This is what the O_SPECIFIC_FD patchset does[1] and I
think it's a reasonable way of solving such problems.

Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH

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