From: Matt Mackall <mpm@selenic.com>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: John Reiser <jreiser@BitWagon.com>,
akpm@linux-foundation.org, tytso@mit.edu,
linux-kernel@vger.kernel.org
Subject: Re: /dev/urandom uses uninit bytes, leaks user data
Date: Sat, 15 Dec 2007 10:30:10 -0600 [thread overview]
Message-ID: <20071215163010.GS19691@waste.org> (raw)
In-Reply-To: <E1J3RD5-0006yU-00@gondolin.me.apana.org.au>
On Sat, Dec 15, 2007 at 03:13:19PM +0800, Herbert Xu wrote:
> John Reiser <jreiser@bitwagon.com> wrote:
> >
> > If speed matters that much, then please recoup 33 cycles on x86
> > by using shifts instead of three divides, such as (gcc 4.1.2):
> >
> > add_entropy_words(r, tmp, (bytes + 3) / 4);
> >
> > 0x8140689 <xfer_secondary_pool+206>: lea 0x3(%esi),%eax
> > 0x814068c <xfer_secondary_pool+209>: mov $0x4,%dl
> > 0x814068e <xfer_secondary_pool+211>: mov %edx,%edi
> > 0x8140690 <xfer_secondary_pool+213>: cltd
> > 0x8140691 <xfer_secondary_pool+214>: idiv %edi
>
> There ought to be a warning about this sort of thing.
Indeed. Seems it would be better to adjust the types appropriately.
Anyway, this is no longer relevant to security@.
--
Mathematics is the supreme nostalgia of our time.
next prev parent reply other threads:[~2007-12-15 16:31 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-14 19:34 /dev/urandom uses uninit bytes, leaks user data John Reiser
2007-12-14 20:13 ` Matt Mackall
2007-12-14 20:45 ` John Reiser
2007-12-14 23:23 ` Theodore Tso
2007-12-15 0:30 ` John Reiser
2007-12-15 4:32 ` Theodore Tso
2007-12-17 16:30 ` John Reiser
2007-12-17 17:36 ` Theodore Tso
2007-12-18 0:52 ` Andy Lutomirski
2007-12-18 3:05 ` Theodore Tso
2007-12-18 3:13 ` David Newall
2007-12-18 3:46 ` Theodore Tso
2007-12-18 4:09 ` David Newall
2007-12-18 4:23 ` Theodore Tso
2007-12-19 22:43 ` Bill Davidsen
2007-12-19 22:40 ` Bill Davidsen
2007-12-20 4:18 ` Andrew Lutomirski
2007-12-20 20:17 ` Phillip Susi
2007-12-21 16:10 ` Andrew Lutomirski
2007-12-22 1:14 ` Theodore Tso
2007-12-26 18:30 ` Phillip Susi
2007-12-20 20:36 ` Theodore Tso
2007-12-27 10:44 ` Pavel Machek
2007-12-18 5:12 ` David Schwartz
2007-12-17 20:59 ` David Schwartz
2007-12-15 7:13 ` Herbert Xu
2007-12-15 16:30 ` Matt Mackall [this message]
2007-12-17 17:28 ` Signed divides vs shifts (Re: [Security] /dev/urandom uses uninit bytes, leaks user data) Linus Torvalds
2007-12-17 17:48 ` Al Viro
2007-12-17 17:55 ` Eric Dumazet
2007-12-17 18:05 ` Ray Lee
2007-12-17 18:10 ` Eric Dumazet
2007-12-17 18:12 ` Ray Lee
2007-12-17 18:23 ` Al Viro
2007-12-17 18:28 ` [Security] Signed divides vs shifts (Re: " Linus Torvalds
2007-12-17 19:08 ` Al Viro
-- strict thread matches above, loose matches on Subject: below --
2007-12-15 7:20 /dev/urandom uses uninit bytes, leaks user data Matti Linnanvuori
2007-12-15 7:54 ` Valdis.Kletnieks
2007-12-15 22:44 linux
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