lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Sat, 14 Jan 2012 13:14:33 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	linux-crypto@...r.kernel.org, netdev@...r.kernel.org,
	ken@...elabs.ch, Steffen Klassert <steffen.klassert@...unet.com>,
	Eric Dumazet <eric.dumazet@...il.com>, security@...nel.org
Subject: Re: [PATCH 2/3] sha512: reduce stack usage to safe number

On Sat, Jan 14, 2012 at 12:41 PM, Alexey Dobriyan <adobriyan@...il.com> wrote:
>
> For the record, it generates "andl $15" here.

Ok. That means that gcc was able to prove that it never had any signed
values (which is certainly reasonable when you do things like "for
(i=0; i<X;i++)"). But it's better to simply not rely on gcc always
getting details like this right.

It's also better to use a model that simply doesn't even require you
as a programmer to have to even *think* about signed values.

It's easy to get "%" wrong by mistake (signed integer modulus didn't
even use to have well-defined semantics in traditional C), and there
is almost never any excuse for using it for powers-of-two.

> Here is updated patch which explicitly uses & (equally tested):

Thanks,

                     Linus
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Powered by blists - more mailing lists