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Date:   Wed, 4 Mar 2020 14:36:59 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Scott Wood <oss@buserror.net>
Cc:     Jason Yan <yanaijie@huawei.com>, pmladek@suse.com,
        rostedt@goodmis.org, sergey.senozhatsky@gmail.com,
        andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk,
        linux-kernel@vger.kernel.org,
        "Tobin C . Harding" <tobin@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Daniel Axtens <dja@axtens.net>
Subject: Re: [PATCH v3 0/6] implement KASLR for powerpc/fsl_booke/64
Message-ID: <202003041433.5E2AAC5@keescook>
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On Wed, Mar 04, 2020 at 03:11:39PM -0600, Scott Wood wrote:
> In any case, this came up now due to a question about what to use when
> printing crash dumps.  PowerPC currently prints stack and return addresses
> with %lx (in addition to %pS in the latter case) and someone proposed

Right -- I think other archs moved entirely to %pS and just removed %lx
and %p uses.

> converting them to %p and/or removing them altogether.  Is there a consensus
> on whether crash dumps need to be sanitized of this stuff as well?  It seems
> like you'd have the addresses in the register dump as well (please don't take
> that away too...).  Maybe crash dumps would be a less problematic place to
> make the hashing conditional (i.e. less likely to break something in userspace
> that wasn't expecting a hash)?

Actual _crash_ dumps print all kinds of stuff, even the KASLR offset,
but for generic stack traces, it's been mainly %pS, with things like
registers using %lx.

I defer to Linus, obviously. I just wanted to repeat what he'd said
before.

-- 
Kees Cook