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Date: Tue, 10 Dec 2013 14:14:09 -0500
From: Vivek Goyal <vgoyal@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>, Kees Cook <keescook@chromium.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Rik van Riel <riel@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Matthew Garrett <matthew.garrett@nebula.com>,
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        Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
        Mel Gorman <mgorman@suse.de>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        kexec@lists.infradead.org
Subject: Re: [PATCH v2] kexec: add sysctl to disable kexec
Message-ID: <20131210191409.GE13909@redhat.com>
References: <20131210001620.GA7938@www.outflux.net>
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On Tue, Dec 10, 2013 at 10:54:00AM -0800, H. Peter Anvin wrote:
> On 12/10/2013 10:33 AM, Vivek Goyal wrote:
> > On Tue, Dec 10, 2013 at 08:32:38AM -0800, H. Peter Anvin wrote:
> >> Of course it isn't.
> > 
> > I am not sure what are you trying to say. This is too brief.
> > 
> > Thanks
> > Vivek
> > 
> 
> Of course it is not sufficient.  Once you can get arbitrary code into
> kernel space (CPL 0) you can do anything, and "disabling jump back" is
> just a speed bump.

Agreed that disabling jump back is only a speed bump.

Kees, so how would be use this knob?

- If I put it in some init script, then root will permission to modify
  and remove it.

- Can one specify sysctl parameters on command line? If yes, then one
  can disable this using kernel command line and in that case kdump will
  be disabled too.

Thanks
Vivek