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From: Andy Lutomirski <luto@amacapital.net>
Date: Fri, 3 Jul 2015 09:57:52 -0700
Message-ID: <CALCETrW2RbX928+TA6YWENNKAx+KY0bjTPHdk72QmPiwphJ1BQ@mail.gmail.com>
Subject: Re: [RFC 0/8] Additional kmsg devices
To: Marcin Niesluchowski <m.niesluchow@samsung.com>
Cc: Richard Weinberger <richard.weinberger@gmail.com>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "open list:ABI/API" <linux-api@vger.kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Petr Mladek <pmladek@suse.cz>, Tejun Heo <tj@kernel.org>,
        Kay Sievers <kay@vrfy.org>, Andrew Morton <akpm@linux-foundation.org>,
        Joe Perches <joe@perches.com>,
        Karol Lewandowski <k.lewandowsk@samsung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
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On Fri, Jul 3, 2015 at 8:09 AM, Marcin Niesluchowski
<m.niesluchow@samsung.com> wrote:
>
> * Message credibility: Lets imagine simple service which collects logs via
> unix sockets. There is no reliable way of identifying logging process.
> getsockopt() with SO_PEERCRED option would give pid form cred structure, but
> according to manual it may not be of actual logging process:
>   "The returned credentials are those that were in effect at the time of the
> call to connect(2) or socketpair(2)."
>       - select(7)

There's SCM_CREDENTIALS, which is dangerous, but it's dangerous in
exactly the same way that your patches are dangerous.  You're
collecting PID/TID when write(2) is called, and it's very easy to get
another process to call write(2) on your behalf, because write(2)
isn't supposed to collect credentials.

--Andy
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