linux-kernel - Re: [PATCH] yama: clarify ptrace

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Message-ID: <CAGXu5jJs-FQT93Og6ULiyugOs1nBCvMKXVrM_dnWTMLKj6ORLg@mail.gmail.com>
Date:   Tue, 2 Oct 2018 14:07:01 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Yves-Alexis Perez <corsac@...sac.net>,
        Jonathan Corbet <corbet@....net>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, trivial@...nel.org
Subject: Re: [PATCH] yama: clarify ptrace_scope=2 in Yama documentation

On Tue, Oct 2, 2018 at 1:52 PM, Matthew Wilcox <willy@...radead.org> wrote:
> On Tue, Oct 02, 2018 at 10:47:23PM +0200, Yves-Alexis Perez wrote:
>> Current phrasing is ambiguous since it's unclear if attaching to a
>> children through PTRACE_TRACEME requires CAP_SYS_PTRACE. Rephrase the
>> sentence to make that clear.
>
> I disagree that your sentence makes that clear.  How about:
>
>>  2 - admin-only attach:
>> -    only processes with ``CAP_SYS_PTRACE`` may use ptrace
>> -    with ``PTRACE_ATTACH``, or through children calling ``PTRACE_TRACEME``.
>> +    only processes with ``CAP_SYS_PTRACE`` may use ptrace, either with
>> +    ``PTRACE_ATTACH`` or through children calling ``PTRACE_TRACEME``.
>
> +    only processes with ``CAP_SYS_PTRACE`` may use ptrace.  This
> +    restricts both ``PTRACE_ATTACH`` and ``PTRACE_TRACEME``.

PTRACE_TRACEME is done by the child, not the process with
CAP_SYS_PTRACE, so I still think the Yves-Alexis's is clearer. But if
other agree, I'm fine with it. :)

-Kees

-- 
Kees Cook
Pixel Security