Date: Wed, 1 Nov 2017 10:16:19 +1100 From: "Tobin C. Harding" <me@...in.cc> To: Joe Perches <joe@...ches.com> Cc: Kees Cook <keescook@...omium.org>, 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>, 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 Mon, Oct 30, 2017 at 07:08:48PM -0700, Joe Perches wrote: > On Tue, 2017-10-31 at 09:33 +1100, Tobin C. Harding wrote: > > On Mon, Oct 30, 2017 at 03:03:21PM -0700, Kees Cook wrote: > > > 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 > > > 18370x > > > > > > 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. > > > > Thanks Kees. V9 leaves SPECIAL out. Also V9 prints the whole 64 bit > > address with the first 32 bits masked to zero. The intent being to _not_ > > change the output format from what it currently is. So it will look like > > this; > > > > 00000000c09e81d0 > > > > What do you think? > > > > Amusingly I think this whole conversation is going to come up again > > when we do %pa, in inverse, since %pa currently does us SPECIAL. > > I once sent a patch set to remove SPECIAL from %pa > and add 0x where necessary. > > https://patchwork.kernel.org/patch/3875471/ > > After that didn't happen, I removed the duplicated > 0x%pa with a sed. > > https://patchwork.kernel.org/patch/8509421/ > > Sending a treewide sed patch would be fine with me. Cool, thanks Joe I'll keep this in mind for when we get to %pa. thanks, Tobin.
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