linux-kernel - Re: [PATCH tip/core/rcu 02/20] torture: Prepare scripting for shift from %p to %pK

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Message-ID: <CAGXu5jJEr4fn047Ce0sKPz-11o_1rNxSGipTO+GUwDQri=d7yw@mail.gmail.com>
Date:   Mon, 11 Dec 2017 11:59:30 -0800
From:   Kees Cook <keescook@...omium.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        David Laight <David.Laight@...lab.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "jiangshanlai@...il.com" <jiangshanlai@...il.com>,
        "dipankar@...ibm.com" <dipankar@...ibm.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "mathieu.desnoyers@...icios.com" <mathieu.desnoyers@...icios.com>,
        "josh@...htriplett.org" <josh@...htriplett.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "dhowells@...hat.com" <dhowells@...hat.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "fweisbec@...il.com" <fweisbec@...il.com>,
        "oleg@...hat.com" <oleg@...hat.com>
Subject: Re: [PATCH tip/core/rcu 02/20] torture: Prepare scripting for shift
 from %p to %pK

On Sun, Dec 10, 2017 at 1:47 PM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
> On Sun, Dec 10, 2017 at 12:39:11PM -0800, Linus Torvalds wrote:
>> I'd rather make %pK act more like %p than have gratuitous differences.

The feature that paranoid folks currently depend on is getting a value
entirely zeroed out with %pK (which is the least possible info leak
risk). The hashed %p is almost just as good except that identical
hashes are still usable to confirm matching values (but the cases
where this would be useful to an attacker are hopefully approaching
zero).

> So it looks like I should drop the three patches in my tree that convert
> %p to %pK.
>
> Any objections?

Sounds good. If they're still useful when hashed, keep the %p. If you
want to remove them because they're sensitive, just remove them
instead of adding new %pK users.

-Kees

-- 
Kees Cook
Pixel Security