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  linux-hardening  linux-cve-announce  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]
Message-ID: <20230509-smirk-viewing-5e13ea0abfeb-mkl@pengutronix.de>
Date: Tue, 9 May 2023 09:06:04 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Vincent MAILHOL <mailhol.vincent@...adoo.fr>
Cc: Frank Jungclaus <Frank.Jungclaus@....eu>,
	Stefan Mätje <Stefan.Maetje@....eu>,
	"linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"wg@...ndegger.com" <wg@...ndegger.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] can: esd_usb: Add support for esd CAN-USB/3

On 09.05.2023 10:28:13, Vincent MAILHOL wrote:
> > > And because hdr.len is initially 3, hdr.len becomes 5. Right? Shouldn't it be 8?
> >
> > It might be a little confusing, but I think it's fine.
> > hdr.len is given in units of longwords (4 bytes each)! Therefore we
> > have 12 bytes (the initial 3 longwords) for struct tx_msg before
> > tx_msg.data[].
> > Than (8 + 3)/4=2 gives us 2 additional longwords for the 8 data bytes.
> > So that 3+2=5 (equal to 20 bytes) should be ok.

I think the term longword is more commonly used in non-Unix operating
systems :)

> OK. So you want to round up the length to the next sizeof(long) multiple, right?
> 
> First, sizeof(long) being platform specific, you need to declare a
> macro to make your intent explicit.
> 
> /* Size of a long int on esd devices */
> #define USB_ESD_SIZEOF_LONG 4
> 
> Please test, but for what I understand, below line is an equivalent
> and a more readable way to achieve your goal:
> 
>           msg->hdr.len = DIV_ROUND_UP(cf->len, USB_ESD_SIZEOF_LONG);

use "sizeof(u32)"

> Also, add documentation to your structure to explain that hdr.len
> represents the length in long, not in bytes.

...lengths in multiple of u32.

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ