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From:   Paul Moore <paul@paul-moore.com>
Date:   Tue, 16 Aug 2022 17:59:41 -0400
Message-ID: <CAHC9VhTmgMfzc+QY8kr+BYQyd_5nEis0Y632w4S2_PGudTRT7g@mail.gmail.com>
Subject: Re: [RFC PATCH v4 0/2] Add capabilities file to securityfs
To:     Francis Laniel <flaniel@linux.microsoft.com>
Cc:     linux-security-module@vger.kernel.org,
        Casey Schaufler <casey@schaufler-ca.com>,
        Eric Biederman <ebiederm@xmission.com>,
        Serge Hallyn <serge@hallyn.com>,
        James Morris <jmorris@namei.org>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:BPF [MISC]" <bpf@vger.kernel.org>
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On Mon, Jul 25, 2022 at 8:42 AM Francis Laniel
<flaniel@linux.microsoft.com> wrote:
> Hi.
>
> First, I hope you are fine and the same for your relatives.

Hi Francis :)

> A solution to this problem could be to add a way for the userspace to ask the
> kernel about the capabilities it offers.
> So, in this series, I added a new file to securityfs:
> /sys/kernel/security/capabilities.
> The goal of this file is to be used by "container world" software to know kernel
> capabilities at run time instead of compile time.

...

> The kernel already exposes the last capability number under:
> /proc/sys/kernel/cap_last_cap

I'm not clear on why this patchset is needed, why can't the
application simply read from "cap_last_cap" to determine what
capabilities the kernel supports?

-- 
paul-moore.com