From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Tom Herbert <tom@herbertland.com>,
Netdev <netdev@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>,
"Daniel J . Bernstein" <djb@cr.yp.to>,
Eric Biggers <ebiggers3@gmail.com>,
David Laight <David.Laight@aculab.com>
Subject: Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function
Date: Wed, 14 Dec 2016 15:30:55 -0800 [thread overview]
Message-ID: <CA+55aFyBGQpEKiAcs0w58ZEie+L8OrWvf_2hvGx4E=L56p5hMg@mail.gmail.com> (raw)
In-Reply-To: <CAHmME9rpvf4tyDjZcJAJxMAW1LcqNm7DiquiYX0uQhRzDLbwqw@mail.gmail.com>
On Wed, Dec 14, 2016 at 2:56 PM, Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> So actually jhash_Nwords makes no sense, since it takes dwords
> (32-bits) not words (16-bits). The siphash analog should be called
> siphash24_Nqwords.
No. The bug is talking about "words" in the first place.
Depending on your background, a "word" can be generally be either 16
bits or 32 bits (or, in some cases, 18 bits).
In theory, a 64-bit entity can be a "word" too, but pretty much nobody
uses that. Even architectures that started out with a 64-bit register
size and never had any smaller historical baggage (eg alpha) tend to
call 32-bit entities "words".
So 16 bits can be a word, but some people/architectures will call it a
"half-word".
To make matters even more confusing, a "quadword" is generally always
64 bits, regardless of the size of "word".
So please try to avoid the use of "word" entirely. It's too ambiguous,
and it's not even helpful as a "size of the native register". It's
almost purely random.
For the kernel, we tend use
- uX for types that have specific sizes (X being the number of bits)
- "[unsigned] long" for native register size
But never "word".
Linus
next prev parent reply other threads:[~2016-12-14 23:30 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-14 3:59 [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Jason A. Donenfeld
2016-12-14 3:59 ` [PATCH v2 2/4] siphash: add convenience functions for jhash converts Jason A. Donenfeld
2016-12-14 3:59 ` [PATCH v2 3/4] secure_seq: use siphash24 instead of md5_transform Jason A. Donenfeld
2016-12-14 12:53 ` Jason A. Donenfeld
2016-12-14 13:16 ` Hannes Frederic Sowa
2016-12-14 13:44 ` Jason A. Donenfeld
2016-12-14 14:47 ` David Laight
2016-12-14 17:49 ` Jason A. Donenfeld
2016-12-14 17:56 ` David Miller
2016-12-14 18:06 ` Jason A. Donenfeld
2016-12-14 19:22 ` Hannes Frederic Sowa
2016-12-14 19:38 ` Jason A. Donenfeld
2016-12-14 20:27 ` Hannes Frederic Sowa
2016-12-14 20:12 ` Tom Herbert
2016-12-14 21:01 ` Jason A. Donenfeld
2016-12-14 3:59 ` [PATCH v2 4/4] random: use siphash24 instead of md5 for get_random_int/long Jason A. Donenfeld
2016-12-14 11:21 ` [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa
2016-12-14 13:10 ` Jason A. Donenfeld
2016-12-14 15:09 ` Hannes Frederic Sowa
2016-12-14 19:47 ` Jason A. Donenfeld
2016-12-15 7:57 ` Herbert Xu
2016-12-15 8:15 ` [kernel-hardening] " Daniel Micay
2016-12-14 12:46 ` Jason A. Donenfeld
2016-12-14 22:03 ` Hannes Frederic Sowa
2016-12-14 23:29 ` Jason A. Donenfeld
2016-12-15 8:31 ` Hannes Frederic Sowa
2016-12-15 11:04 ` David Laight
2016-12-15 12:23 ` Hannes Frederic Sowa
2016-12-15 12:28 ` David Laight
2016-12-15 12:50 ` Hannes Frederic Sowa
2016-12-15 13:56 ` David Laight
2016-12-15 14:56 ` Hannes Frederic Sowa
2016-12-15 15:41 ` David Laight
2016-12-15 15:53 ` Hannes Frederic Sowa
2016-12-15 18:50 ` Jason A. Donenfeld
2016-12-15 20:31 ` Hannes Frederic Sowa
2016-12-15 20:43 ` Jason A. Donenfeld
2016-12-15 21:04 ` Peter Zijlstra
2016-12-15 21:09 ` Hannes Frederic Sowa
2016-12-15 21:17 ` Hannes Frederic Sowa
2016-12-15 21:09 ` Peter Zijlstra
2016-12-15 21:11 ` [kernel-hardening] " Jason A. Donenfeld
2016-12-15 21:14 ` Linus Torvalds
2016-12-14 18:46 ` [PATCH v3 1/3] " Jason A. Donenfeld
2016-12-14 18:46 ` [PATCH v3 2/3] secure_seq: use siphash24 instead of md5_transform Jason A. Donenfeld
2016-12-14 21:44 ` kbuild test robot
2016-12-14 18:46 ` [PATCH v3 3/3] random: use siphash24 instead of md5 for get_random_int/long Jason A. Donenfeld
2016-12-14 21:56 ` kbuild test robot
2016-12-14 21:57 ` kbuild test robot
2016-12-15 10:14 ` David Laight
2016-12-15 18:51 ` Jason A. Donenfeld
2016-12-14 19:18 ` [PATCH v3 1/3] siphash: add cryptographically secure hashtable function Tom Herbert
2016-12-14 19:35 ` Jason A. Donenfeld
2016-12-14 20:55 ` Jason A. Donenfeld
2016-12-14 21:35 ` Tom Herbert
2016-12-14 22:56 ` Jason A. Donenfeld
2016-12-14 23:14 ` Tom Herbert
2016-12-14 23:17 ` Jason A. Donenfeld
2016-12-18 0:06 ` Christian Kujau
2016-12-14 23:30 ` Linus Torvalds [this message]
2016-12-14 23:34 ` Jason A. Donenfeld
2016-12-15 0:10 ` Linus Torvalds
2016-12-15 10:22 ` David Laight
2016-12-14 21:15 ` kbuild test robot
2016-12-14 21:21 ` Jason A. Donenfeld
2016-12-15 1:46 ` [PATCH v4 1/4] " Jason A. Donenfeld
2016-12-15 1:46 ` [PATCH v4 2/4] siphash: add N[qd]word helpers Jason A. Donenfeld
2016-12-15 1:46 ` [PATCH v4 3/4] secure_seq: use siphash instead of md5_transform Jason A. Donenfeld
2016-12-15 1:46 ` [PATCH v4 4/4] random: use siphash instead of MD5 for get_random_int/long Jason A. Donenfeld
2016-12-15 4:23 ` [PATCH v4 1/4] siphash: add cryptographically secure hashtable function kbuild test robot
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