linux-kernel - Re: [kernel-hardening] Re: [PATCH v6 0/2] security: tty: make TIOCSTI ioctl require CAP_SYS

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Message-ID: <1494450134.28559.2.camel@gmail.com>
Date:   Wed, 10 May 2017 17:02:14 -0400
From:   Daniel Micay <danielmicay@...il.com>
To:     Alan Cox <gnomes@...rguk.ukuu.org.uk>, Matt Brown <matt@...tt.com>
Cc:     serge@...lyn.com, gregkh@...uxfoundation.org, jslaby@...e.com,
        akpm@...ux-foundation.org, jannh@...gle.com, keescook@...omium.org,
        jmorris@...ei.org, kernel-hardening@...ts.openwall.com,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [kernel-hardening] Re: [PATCH v6 0/2] security: tty: make
 TIOCSTI ioctl require CAP_SYS_ADMIN

On Wed, 2017-05-10 at 21:29 +0100, Alan Cox wrote:
> 
> In addition your change to allow it to be used by root in the guest
> completely invalidates any protection you have because I can push
> 
> "rm -rf /\n"
> 
> as root in my namespace and exit
> 
> The tty buffers are not flushed across the context change so the shell
> you return to gets the input and oh dear....
> 
> Alan

I might be missing something, but it looks like the patch tracks where
the tty was created and only allows this with CAP_SYS_ADMIN in the ns
where the tty came from.