Re: [kernel-hardening] [RFC 0/4] make call_usermodehelper a bit more "safe"

Jason A. Donenfeld
2016-12-14T21:28:25Z

Hi Greg,

On Wed, Dec 14, 2016 at 7:50 PM, Greg KH <gregkh@linuxfoundation.org> wrote:
> So, anyone have any better ideas? Is this approach worth it? Or should
> we just go down the "whitelist" path?

I think your approach is generally better than the whitelist path. But
maybe there's yet a third approach that involves futzing with page
permissions at runtime. I think grsec does something similar with
read_mostly function pointer structs. Namely, they make them read-only
const, and then temporarily twiddle the page permissions if it needs
to be changed while disabling preemption. There could be a particular
class of data that needs to be "opened" and "closed" in order to
modify. Seems like these strings would be a good use of that.

Jason