linux-kernel - Re: [PATCH v8 4/4] vsprintf: Add command line option debug_boot_weak

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <e4f6bfb3-68c7-9f57-0d90-d68d0913234a@infradead.org>
Date:   Wed, 20 Jun 2018 09:09:49 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     "Tobin C. Harding" <me@...in.cc>, Theodore Ts'o <tytso@....edu>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Kees Cook <keescook@...omium.org>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 4/4] vsprintf: Add command line option
 debug_boot_weak_hash

On 06/19/2018 09:20 PM, Tobin C. Harding wrote:
> Currently printing [hashed] pointers requires enough entropy to be
> available.  Early in the boot sequence this may not be the case
> resulting in a dummy string '(____ptrval____)' being printed.  This
> makes debugging the early boot sequence difficult.  We can relax the
> requirement to use cryptographically secure hashing during debugging.
> This enables debugging while keeping development/production kernel
> behaviour the same.
> 
> If new command line option debug_boot_weak_hash is enabled use
> cryptographically insecure hashing and hash pointer value immediately.
> 
> Signed-off-by: Tobin C. Harding <me@...in.cc>
> Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  9 +++++++++
>  lib/vsprintf.c                                  | 17 +++++++++++++++++
>  2 files changed, 26 insertions(+)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 638342d0a095..a116fc0366b0 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -748,6 +748,15 @@
>  
>  	debug		[KNL] Enable kernel debugging (events log level).
>  
> +	debug_boot_weak_hash
> +			[KNL] Enable printing pointers early in the boot
> +			sequence.  If enabled, we use a weak hash instead of
> +			siphash to hash pointers.  Use this option if you need
> +			to see pointer values during early boot (i.e you are

maybe:
			to see hashed pointer values
i.e., not raw pointers.

> +			seeing instances of '(___ptrval___)').
> +			Cryptographically insecure, please do not use on
> +			production kernels.
> +
>  	debug_locks_verbose=
>  			[KNL] verbose self-tests
>  			Format=<0|1>

thanks,
-- 
~Randy