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Date: Tue, 23 May 2017 12:50:25 -0700
From: Andy Lutomirski <>
To: Kees Cook <>
Cc: Solar Designer <>, Djalal Harouni <>, 
	linux-kernel <>, Network Development <>, 
	LSM List <>, 
	"" <>, Andy Lutomirski <>, 
	Andrew Morton <>, Rusty Russell <>, 
	"Serge E. Hallyn" <>, Jessica Yu <>, 
	"David S. Miller" <>, James Morris <>, 
	Paul Moore <>, Stephen Smalley <>, 
	Greg Kroah-Hartman <>, 
	Tetsuo Handa <>, Ingo Molnar <>, 
	Linux API <>, Dongsu Park <>, 
	Casey Schaufler <>, Jonathan Corbet <>, 
	Arnaldo Carvalho de Melo <>, Mauro Carvalho Chehab <>, 
	Peter Zijlstra <>, Zendyani <>, 
	"open list:DOCUMENTATION" <>, Al Viro <>, 
	Ben Hutchings <>
Subject: Re: [PATCH v4 next 0/3] modules: automatic module
 loading restrictions

On Tue, May 23, 2017 at 11:36 AM, Kees Cook <> wrote:
> On Tue, May 23, 2017 at 12:48 AM, Solar Designer <> wrote:
>> For modules_autoload_mode=2, we already seem to have the equivalent of
>> modprobe=/bin/true (or does it differ subtly, maybe in return values?),
>> which I already use at startup on a GPU box like this (preloading
>> modules so that the OpenCL backends wouldn't need the autoloading):
>> nvidia-smi
>> nvidia-modprobe -u -c=0
>> #modprobe nvidia_uvm
>> #modprobe fglrx
>> sysctl -w kernel.modprobe=/bin/true
>> sysctl -w kernel.hotplug=/bin/true
>> but it's good to also have this supported more explicitly and more
>> consistently through modules_autoload_mode=2 while we're at it.  So I
>> support having this mode as well.  I just question the need to have it
>> non-resettable.
> I agree it's useful to have the explicit =2 state just to avoid
> confusion when more systems start implementing
> CONFIG_STATIC_USERMODEHELPER and kernel.modprobe becomes read-only
> (though the userspace implementation may allow for some way to disable
> it, etc). I just like avoiding the upcall to modprobe at all.

I fully support =2 to mean "no automatic loading at all".  I dislike
making it non-resettable.  If you can write to sysctls, then, most
likely you can either call init_module() directly or the system has
module loading disabled entirely.

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