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From: Dan Carpenter <>
To: Daniel Borkmann <>
	Hannes Frederic Sowa <>,
	Alexey Dobriyan <>,
	Kees Cook <>,
	Julia Lawall <>
Subject: Re: [PATCH] random: add and use memzero_explicit() for clearing data
Date: Mon, 1 Dec 2014 13:27:39 +0300	[thread overview]
Message-ID: <20141201102529.GA9666@mwanda> (raw)
In-Reply-To: <>

On Mon, Aug 25, 2014 at 10:01:39PM +0200, Daniel Borkmann wrote:
> zatimend has reported that in his environment (3.16/gcc4.8.3/corei7)
> memset() calls which clear out sensitive data in extract_{buf,entropy,
> entropy_user}() in random driver are being optimized away by gcc.
> Add a helper memzero_explicit() (similarly as explicit_bzero() variants)
> that can be used in such cases where a variable with sensitive data is
> being cleared out in the end. Other use cases might also be in crypto
> code. [ I have put this into lib/string.c though, as it's always built-in
> and doesn't need any dependencies then. ]
> Fixes kernel bugzilla: 82041


That's not ok.  We totally rely on memset to work.  Every single memset
that I have added was absolutely necessary.  This should be fixed
so that memset works instead of adding a work around for specific

dan carpnter

  parent reply	other threads:[~2014-12-01 10:28 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-25 20:01 [PATCH] random: add and use memzero_explicit() for clearing data Daniel Borkmann
2014-08-25 20:35 ` Alexey Dobriyan
2014-08-25 20:38   ` Daniel Borkmann
2014-08-25 23:11 ` Hannes Frederic Sowa
2014-08-27  3:21   ` Theodore Ts'o
2014-12-01 10:27 ` Dan Carpenter [this message]
2014-12-01 11:04   ` Daniel Borkmann
2014-12-01 11:29     ` Dan Carpenter
2014-12-01 11:38       ` Dan Carpenter
2014-12-01 13:39         ` Daniel Borkmann
2014-12-01 11:48       ` Daniel Borkmann

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