linux-kernel - Re: [PATCH V8 0/2] printk: hash addresses printed with %p

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Message-ID: <1509492793.31043.12.camel@perches.com>
Date:   Tue, 31 Oct 2017 16:33:13 -0700
From:   Joe Perches <joe@...ches.com>
To:     "Tobin C. Harding" <me@...in.cc>
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>,
        Vinod Koul <vinod.koul@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: Re: [PATCH V8 0/2] printk: hash addresses printed with %p

On Wed, 2017-11-01 at 10:16 +1100, Tobin C. Harding wrote:
> 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.

fyi:  There are more of these misuses of 0x%pa now:

$ git grep -E -n "0[xX]%pa[dp]?\b"
drivers/dma/at_hdmac_regs.h:388:                 "  desc: s%pad d%pad ctrl0x%x:0x%x l0x%pad\n",
drivers/dma/coh901318.c:1322:           dev_vdbg(COHC_2_DEV(cohc), "i %d, lli %p, ctrl 0x%x, src 0x%pad"
drivers/dma/coh901318.c:1323:                    ", dst 0x%pad, link 0x%pad virt_link_addr 0x%p\n",
drivers/dma/coh901318.c:2234:            "[%s] channel %d src 0x%pad dest 0x%pad size %zu\n",
drivers/media/platform/sti/delta/delta-mem.c:35:                "%s allocate %d bytes of HW memory @(virt=0x%p, phy=0x%pad): %s\n",
drivers/media/platform/sti/delta/delta-mem.c:46:                "%s     free %d bytes of HW memory @(virt=0x%p, phy=0x%pad): %s\n",
drivers/media/platform/sti/delta/delta-v4l2.c:1147:             dev_dbg(delta->dev, "%s au[%d] prepared; virt=0x%p, phy=0x%pad\n",
drivers/media/platform/sti/delta/delta-v4l2.c:1503:                     "%s frame[%d] prepared; virt=0x%p, phy=0x%pad\n",
drivers/media/platform/stm32/stm32-dcmi.c:486:          dev_dbg(dcmi->dev, "buffer[%d] phy=0x%pad size=%zu\n",
drivers/media/platform/ti-vpe/cal.c:496:        cal_info(dev, "CAL Registers @ 0x%pa:\n", &dev->res->start);