linux-kernel - Re: [PATCH v5] printk: hash addresses printed with %p

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Date:   Thu, 19 Oct 2017 10:18:01 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     "Tobin C. Harding" <me@...in.cc>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.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>, Joe Perches <joe@...ches.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>
Subject: Re: [PATCH v5] printk: hash addresses printed with %p

On Wed, Oct 18, 2017 at 10:49 PM, Jason A. Donenfeld <Jason@...c4.com> wrote:
> static void fill_random_ptr_key(struct random_ready_callback *rdy)
> {
>     get_random_bytes(&ptr_secret, sizeof(ptr_secret));
>     static_branch_disable(&no_ptr_secret);
> }
>
> static struct random_ready_callback random_ready = {
>     .func = fill_random_ptr_key
> };
>
> static int __init initialize_ptr_random(void)
> {
>     int ret = add_random_ready_callback(&random_ready);
>
>     if (!ret)
>         return 0;
>     else if (ret == -EALREADY) {
>         fill_random_ptr_key(&random_ready);
>         return 0;
>     }
>
>     return ret;
> }
> early_initcall(initialize_ptr_random);

Tangent: why is the random_ready API designed with -EALREADY? Couldn't
add_random_ready_callback() just perform the call itself and avoid
needing all the callers to check for -EALREADY?

-Kees

-- 
Kees Cook
Pixel Security