linux-kernel - Re: [PATCH] ELF: implement AT

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Message-Id: <20081006235827.59306154271@magilla.localdomain>
Date:	Mon,  6 Oct 2008 16:58:27 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Kees Cook <kees.cook@...onical.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Jakub Jelinek <jakub@...hat.com>,
	Ulrich Drepper <drepper@...hat.com>, libc-alpha@...rceware.org
Subject: Re: [PATCH] ELF: implement AT_RANDOM for future glibc use

What mmap randomization and stack randomization actually use is
get_random_int(), not get_random_bytes().  This is one of those weaker
flavors seeded occasionally from the real entropy pool.  (As is, it's not a
good choice for getting 16 bytes of random at once, since it usually
returns the same 4 bytes each time when called 4 times in quick succession.)

What glibc wants is some bits with a strength of randomness chosen by the
kernel, and not to worry about the details.  I think the strength applied
to mmap and stack randomization is good enough for AT_RANDOM.

Thanks,
Roland
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