Date: Mon, 30 Oct 2017 15:03:21 -0700 From: Kees Cook <keescook@...omium.org> To: "Tobin C. Harding" <me@...in.cc> Cc: kernel-hardening@...ts.openwall.com, "Jason A. Donenfeld" <Jason@...c4.com>, "Theodore Ts'o" <tytso@....edu>, Linus Torvalds <torvalds@...ux-foundation.org>, Paolo Bonzini <pbonzini@...hat.com>, Tycho Andersen <tycho@...ker.com>, "Roberts, William C" <william.c.roberts@...el.com>, Tejun Heo <tj@...nel.org>, Jordan Glover <Golden_Miller83@...tonmail.ch>, Greg KH <gregkh@...uxfoundation.org>, Petr Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>, Ian Campbell <ijc@...lion.org.uk>, Sergey Senozhatsky <sergey.senozhatsky@...il.com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <wilal.deacon@....com>, Steven Rostedt <rostedt@...dmis.org>, Chris Fries <cfries@...gle.com>, Dave Weinstein <olorin@...gle.com>, Daniel Micay <danielmicay@...il.com>, Djalal Harouni <tixxdz@...il.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH V8 0/2] printk: hash addresses printed with %p On Wed, Oct 25, 2017 at 7:53 PM, Tobin C. Harding <me@...in.cc> wrote: > Here is the behaviour that this set implements. > > For kpt_restrict==0 > > Randomness not ready: > printed with %p: (pointer) # NOTE: with padding > Valid pointer: > printed with %pK: deadbeefdeadbeef > printed with %p: 0xdeadbeef > malformed specifier (eg %i): 0xdeadbeef I really think we can't include SPECIAL unless _every_ callsite of %p is actually doing "0x%p", and then we're replacing all of those. We're not doing that, though... $ git grep '%p\b' | wc -l 12766 $ git grep '0x%p\b' | wc -l 1837 If we need some kind of special marking that this is a hashed variable, that should be something other than "0x". If we're using the existing "(null)" and new "(pointer)" text, maybe "(hash:xxxxxx)" should be used instead? Then the (rare) callers with 0x become "0x(hash:xxxx)" and naked callers produce "(hash:xxxx)". I think the first step for this is to just leave SPECIAL out. -Kees -- Kees Cook Pixel Security
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