> -----Original Message----- > From: keesc...@google.com [mailto:keesc...@google.com] On Behalf Of Kees > Cook > Sent: Wednesday, November 29, 2017 2:28 PM > To: David Laight <david.lai...@aculab.com> > Cc: Linus Torvalds <torva...@linux-foundation.org>; Tobin C. Harding > <m...@tobin.cc>; kernel-harden...@lists.openwall.com; Jason A. Donenfeld > <ja...@zx2c4.com>; Theodore Ts'o <ty...@mit.edu>; Paolo Bonzini > <pbonz...@redhat.com>; Tycho Andersen <ty...@tycho.ws>; Roberts, William C > <william.c.robe...@intel.com>; Tejun Heo <t...@kernel.org>; Jordan Glover > <golden_mille...@protonmail.ch>; Greg KH <gre...@linuxfoundation.org>; > Petr Mladek <pmla...@suse.com>; Joe Perches <j...@perches.com>; Ian > Campbell <i...@hellion.org.uk>; Sergey Senozhatsky > <sergey.senozhat...@gmail.com>; Catalin Marinas <catalin.mari...@arm.com>; > Will Deacon <wilal.dea...@arm.com>; Steven Rostedt <rost...@goodmis.org>; > Chris Fries <cfr...@google.com>; Dave Weinstein <olo...@google.com>; Daniel > Micay <danielmi...@gmail.com>; Djalal Harouni <tix...@gmail.com>; Radim > Krcmár <rkrc...@redhat.com>; Linux Kernel Mailing List <linux- > ker...@vger.kernel.org>; Network Development <netdev@vger.kernel.org>; > David Miller <da...@davemloft.net>; Stephen Rothwell > <s...@canb.auug.org.au>; Andrey Ryabinin <aryabi...@virtuozzo.com>; > Alexander Potapenko <gli...@google.com>; Dmitry Vyukov > <dvyu...@google.com>; Andrew Morton <a...@linux-foundation.org> > Subject: Re: [PATCH V11 4/5] vsprintf: add printk specifier %px > > On Wed, Nov 29, 2017 at 2:07 AM, David Laight <david.lai...@aculab.com> > wrote: > > From: Linus Torvalds > >> Sent: 29 November 2017 02:29 > >> > >> On Tue, Nov 28, 2017 at 6:05 PM, Tobin C. Harding <m...@tobin.cc> wrote: > >> > > >> > Let's add specifier %px as a > >> > clear, opt-in, way to print a pointer and maintain some level of > >> > isolation from all the other hex integer output within the Kernel. > >> > >> Yes, I like this model. It's easy and it's obvious ("'x' for hex"), > >> and it gives people a good way to say "yes, I really want the actual > >> address as hex" for if/when the hashed pointer doesn't work for some > >> reason. > > > > Remind me to change every %p to %px on kernels that support it. > > > > Although the absolute values of pointers may not be useful, knowing > > that two pointer differ by a small amount is useful. > > It is also useful to know whether pointers are to stack, code, static > > data or heap. > > > > This change to %p is going to make debugging a nightmare. > > In the future, maybe we could have a knob: unhashed, hashed (default), or > zeroed.
Isn't that just kptr_restrict and get us right back to the simpler patches I proposed? > > -Kees > > -- > Kees Cook > Pixel Security
