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Date:   Thu, 30 Apr 2020 11:54:29 +1000
From:   Aleksa Sarai <cyphar@cyphar.com>
To:     =?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?= <mic@digikod.net>
Cc:     linux-kernel@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
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        =?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?= <mickael.salaun@ssi.gouv.fr>,
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Subject: Re: [PATCH v3 0/5] Add support for RESOLVE_MAYEXEC
Message-ID: <20200430015429.wuob7m5ofdewubui@yavin.dot.cyphar.com>
References: <20200428175129.634352-1-mic@digikod.net>
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On 2020-04-28, Micka=EBl Sala=FCn <mic@digikod.net> 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.
>=20
> 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.

--=20
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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