RE: [PATCH V11 0/5] hash addresses printed with %p

From: Andrew Morton

Sent: 29 November 2017 23:21

quoted

The added advantage of hashing %p is that security is now opt-out, if
you _really_ want the address you have to work a little harder and use
%px.

You need a system-wide opt-out that prints the actual values.
Otherwise developers will use something else to print addresses and
the code will remain in the released drivers.

quoted

The idea for creating the printk specifier %px to print the actual
address was suggested by Kees Cook (see below for email threads by
subject).

Maybe I'm being thick, but...  if we're rendering these addresses
unusable by hashing them, why not just print something like
"<obscured>" in their place?  That loses the uniqueness thing but I
wonder how valuable that is in practice?

My worry is that is you get a kernel 'oops' print with actual register
values you have no easy way of tying an address or address+offset to
the corresponding hash(address) printed elsewhere.

	David