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    SubjectRE: [PATCH V11 4/5] vsprintf: add printk specifier %px
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    > -----Original Message-----
    > From: keescook@google.com [mailto:keescook@google.com] On Behalf Of Kees
    > Cook
    > Sent: Wednesday, November 29, 2017 2:28 PM
    > To: David Laight <David.Laight@aculab.com>
    > Cc: Linus Torvalds <torvalds@linux-foundation.org>; Tobin C. Harding
    > <me@tobin.cc>; kernel-hardening@lists.openwall.com; Jason A. Donenfeld
    > <Jason@zx2c4.com>; Theodore Ts'o <tytso@mit.edu>; Paolo Bonzini
    > <pbonzini@redhat.com>; Tycho Andersen <tycho@tycho.ws>; Roberts, William C
    > <william.c.roberts@intel.com>; Tejun Heo <tj@kernel.org>; Jordan Glover
    > <Golden_Miller83@protonmail.ch>; Greg KH <gregkh@linuxfoundation.org>;
    > Petr Mladek <pmladek@suse.com>; Joe Perches <joe@perches.com>; Ian
    > Campbell <ijc@hellion.org.uk>; Sergey Senozhatsky
    > <sergey.senozhatsky@gmail.com>; Catalin Marinas <catalin.marinas@arm.com>;
    > Will Deacon <wilal.deacon@arm.com>; Steven Rostedt <rostedt@goodmis.org>;
    > Chris Fries <cfries@google.com>; Dave Weinstein <olorin@google.com>; Daniel
    > Micay <danielmicay@gmail.com>; Djalal Harouni <tixxdz@gmail.com>; Radim
    > Krcmár <rkrcmar@redhat.com>; Linux Kernel Mailing List <linux-
    > kernel@vger.kernel.org>; Network Development <netdev@vger.kernel.org>;
    > David Miller <davem@davemloft.net>; Stephen Rothwell
    > <sfr@canb.auug.org.au>; Andrey Ryabinin <aryabinin@virtuozzo.com>;
    > Alexander Potapenko <glider@google.com>; Dmitry Vyukov
    > <dvyukov@google.com>; Andrew Morton <akpm@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.Laight@aculab.com>
    > wrote:
    > > From: Linus Torvalds
    > >> Sent: 29 November 2017 02:29
    > >>
    > >> On Tue, Nov 28, 2017 at 6:05 PM, Tobin C. Harding <me@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
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