linux-kernel - Re: [PATCH v3 1/4] seccomp: Add sysctl to display available actions

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Message-ID: <b02e5db8-08d4-752b-2f85-4f4e0a5799ed@canonical.com>
Date:   Thu, 16 Feb 2017 12:47:05 -0600
From:   Tyler Hicks <tyhicks@...onical.com>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Paul Moore <paul@...l-moore.com>, Eric Paris <eparis@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Will Drewry <wad@...omium.org>, linux-audit@...hat.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        John Crispin <john@...ozen.org>
Subject: Re: [PATCH v3 1/4] seccomp: Add sysctl to display available actions

On 02/15/2017 09:14 PM, Andy Lutomirski wrote:
> On Mon, Feb 13, 2017 at 7:45 PM, Tyler Hicks <tyhicks@...onical.com> wrote:
>> This patch creates a read-only sysctl containing an ordered list of
>> seccomp actions that the kernel supports. The ordering, from left to
>> right, is the lowest action value (kill) to the highest action value
>> (allow). Currently, a read of the sysctl file would return "kill trap
>> errno trace allow". The contents of this sysctl file can be useful for
>> userspace code as well as the system administrator.
> 
> Would this make more sense as a new seccomp(2) mode a la
> SECCOMP_HAS_ACTION?  Then sandboxy things that have no fs access could
> use it.
> 

It would make sense for code that needs to check which actions are
available. It wouldn't make sense for administrators that need to check
which actions are available unless libseccomp provided a wrapper utility.

Is this a theoretical concern or do you know of a sandboxed piece of
code that cannot access the sysctl before constructing a seccomp filter?

Tyler



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