On Wed, 29 Nov 2017 13:05:00 +1100 "Tobin C. Harding" <m...@tobin.cc> wrote:
> Currently there exist approximately 14 000 places in the Kernel where > addresses are being printed using an unadorned %p. This potentially > leaks sensitive information regarding the Kernel layout in memory. Many > of these calls are stale, instead of fixing every call lets hash the > address by default before printing. This will of course break some > users, forcing code printing needed addresses to be updated. We can add > a printk specifier for this purpose (%px) to give developers a clear > upgrade path for breakages caused by applying this patch set. > > 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. > > 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?
