linux-kernel - Re: [kernel-hardening] Re: [PATCH v7 2/2] security: tty: make TIOCSTI ioctl require CAP_SYS

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Message-ID: <cb0daac8-bd8d-0780-cf04-46033f8fea10@nmatt.com>
Date:   Wed, 31 May 2017 00:10:17 -0400
From:   Matt Brown <matt@...tt.com>
To:     James Morris <jmorris@...ei.org>,
        Boris Lukashev <blukashev@...pervictus.com>
Cc:     Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Greg KH <gregkh@...uxfoundation.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Kees Cook <keescook@...omium.org>,
        kernel-hardening@...ts.openwall.com,
        linux-security-module <linux-security-module@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [kernel-hardening] Re: [PATCH v7 2/2] security: tty: make TIOCSTI
 ioctl require CAP_SYS_ADMIN

On 05/30/2017 10:48 PM, James Morris wrote:
> On Mon, 29 May 2017, Boris Lukashev wrote:
>
>> With all due respect sir, i believe your review falls short of the
>> purpose of this effort - to harden the kernel against flaws in
>> userspace.
>
> Which effort?  Kernel self protection is about protecting against flaws in
> the kernel.
>
> See:
> https://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project
>
>   "This project starts with the premise that kernel bugs have a very long
>    lifetime, and that the kernel must be designed in ways to protect against
>    these flaws."
>
> We need to avoid conflating:
>
> - hardening the kernel against attack; and
> - modifying the kernel to try and harden userspace.
>
> These patches are the latter, and the case for them is not as
> straightforward.
>
>
> - James
>

I agree that these patches aren't kernel self protection and I don't
believe I have claimed they are such a thing. These patches I'm
presenting are more akin to ptrace protections that are found in Yama.