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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);
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