linux-kernel - Re: [BUG/PATCH] kernel RNG and its secrets

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]

Date:	Fri, 10 Apr 2015 16:09:10 +0200
From:	Stephan Mueller <smueller@...onox.de>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	Daniel Borkmann <daniel@...earbox.net>, mancha <mancha1@...o.com>,
	tytso@....edu, linux-kernel@...r.kernel.org,
	linux-crypto@...r.kernel.org, herbert@...dor.apana.org.au,
	dborkman@...hat.com
Subject: Re: [BUG/PATCH] kernel RNG and its secrets

Am Freitag, 10. April 2015, 16:00:03 schrieb Hannes Frederic Sowa:

Hi Hannes,

>On Fr, 2015-04-10 at 15:25 +0200, Stephan Mueller wrote:
>> I would like to bring up that topic again as I did some more analyses:
>> 
>> For testing I used the following code:
>> 
>> static inline void memset_secure(void *s, int c, size_t n)
>> {
>> 
>>         memset(s, c, n);
>> 	
>> 	BARRIER
>> 
>> }
>> 
>> where BARRIER is defined as:
>> 
>> (1) __asm__ __volatile__("" : "=r" (s) : "0" (s));
>> 
>> (2) __asm__ __volatile__("": : :"memory");
>> 
>> (3) __asm__ __volatile__("" : "=r" (s) : "0" (s) : "memory");
>
>Hm, I wonder a little bit...
>
>Could you quickly test if you replace (s) with (n) just for the fun of
>it? I don't know if we should ask clang people about that, at least it
>is their goal to be as highly compatible with gcc inline asm.

Using 

 __asm__ __volatile__("" : "=r" (n) : "0" (n) : "memory");

clang O2/3: no mov

gcc O2/3: mov present

==> not good


Using
 __asm__ __volatile__("" : "=r" (n) : "0" (n));

clang O2/3: no mov

gcc O2/3: no mov


==> not good


What do you expect that change shall do?

>
>Thanks for looking into this!
>
>Bye,
>Hannes


Ciao
Stephan
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/