linux-kernel - Re: [PATCH v3 0/6] implement KASLR for powerpc/fsl

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Message-ID: <202003041433.5E2AAC5@keescook>
Date:   Wed, 4 Mar 2020 14:36:59 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Scott Wood <oss@...error.net>
Cc:     Jason Yan <yanaijie@...wei.com>, pmladek@...e.com,
        rostedt@...dmis.org, sergey.senozhatsky@...il.com,
        andriy.shevchenko@...ux.intel.com, linux@...musvillemoes.dk,
        linux-kernel@...r.kernel.org,
        "Tobin C . Harding" <tobin@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Daniel Axtens <dja@...ens.net>
Subject: Re: [PATCH v3 0/6] implement KASLR for powerpc/fsl_booke/64

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