linux-kernel - Re: [PATCH] random: add and use memzero

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Message-ID: <547C6F88.9000206@redhat.com>
Date:	Mon, 01 Dec 2014 14:39:20 +0100
From:	Daniel Borkmann <dborkman@...hat.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
CC:	tytso@....edu, zatimend@...mail.co.uk,
	linux-kernel@...r.kernel.org,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Julia Lawall <julia.lawall@...6.fr>
Subject: Re: [PATCH] random: add and use memzero_explicit() for clearing data

On 12/01/2014 12:38 PM, Dan Carpenter wrote:
> On Mon, Dec 01, 2014 at 02:29:57PM +0300, Dan Carpenter wrote:
>> On Mon, Dec 01, 2014 at 12:04:57PM +0100, Daniel Borkmann wrote:
>>> Well, BSD has helpers such as bzero_explicit() for such cases to work
>>> around this, which memzero_explicit() similarly does; see also [1].
>>>
>>>    [1] https://gcc.gnu.org/ml/gcc-help/2014-10/msg00059.html
>>
>> We should make memset() a define and call a custom function internally.
>
> Or we could specify -fno-builtin-memset like the GCC people suggest.

If there's a better, reliable way, I'm all for it. To me, memzero_explicit()
seemed like the least intrusive variant doing the job, I'm unsure if globally
setting -fno-builtin-memset will come with unforeseen side-effects on some
archs (besides performance-wise).
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