netdev - [PATCH net-2.6] can: Fix data length code handling in rx path

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Date:	Sat, 12 Dec 2009 15:13:21 +0100
From:	Oliver Hartkopp <oliver@...tkopp.net>
To:	David Miller <davem@...emloft.net>
CC:	Wolfgang Grandegger <wg@...ndegger.com>,
	Linux Netdev List <netdev@...r.kernel.org>,
	SocketCAN Core Mailing List <socketcan-core@...ts.berlios.de>
Subject: [PATCH net-2.6] can: Fix data length code handling in rx path

A valid CAN dataframe can have a data length code (DLC) of 0 .. 8 data bytes.

When reading the CAN controllers register the 4-bit value may contain values
from 0 .. 15 which may exceed the reserved space in the socket buffer!

The ISO 11898-1 Chapter 8.4.2.3 (DLC field) says that register values > 8
should be reduced to 8 without any error reporting or frame drop.

This patch introduces a new helper macro to cast a given 4-bit data length
code (dlc) to __u8 and ensure the DLC value to be max. 8 bytes.

The different handlings in the rx path of the CAN netdevice drivers are fixed.

Signed-off-by: Oliver Hartkopp <oliver@...tkopp.net>

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View attachment "can_dlc_rx_path_fixup.patch" of type "text/x-patch" (5822 bytes)