On Tue, Nov 28, 2017 at 03:29:01PM -0800, Kees Cook wrote:

quoted

So in these two cases, if the kernel was built w/o modules, and HDLC
and DCCP was built-in, you'd be screwed, then?

Sure, but that's not the common situation.

quoted

Is the goal here to protect people using distro kernels which build
the world as modules, including dodgy pieces of kernel code that are
bug-ridden?

The bulk of the risk comes from distro kernels, yes. (Though "bug
ridden" is a strong statement. There are and will be bugs, scattered
across a wide portion of the kernel, it's just that modules tend to
cover most of that attack surface.)

OK, but if the goal is to protect users who are running distro
kernels, then a kernel config that breaks some percentage of users is
****highly**** unlikely to be enabled by Red Hat and SuSE, right?  And
many of these users either can't (from a skills perspective) or won't
(because they lose all support from the enterprise distro's help desk)
recompile their kernel to enable an "might break 3% of all users ---
oh, well" config option.

Which argues for being extremely conservative about making something
that has an extremely low probability of breaking users, and it points
out why Geo Kozey's "who cares about breaking users; security is
IMPORTANT" argument is so wrong-headed.

If the goal is to protect distro kernels, but a sloppy approach
guarantees that distro kernels will never enable it, is it really
worth it?

	   	       	       	    	  	 - Ted

P.S.  This is where it might be useful to get some input from the Red
Hat and SuSE support teams.  How many angry user calls to their help
desk are they willing to field before they'll just turn off the kernel
config option for their kernels?
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