From c7cd606f60e7679c7f9eee7010f02a6f000209c1 Mon Sep 17 00:00:00 2001 From: Oliver Hartkopp Date: Sat, 12 Dec 2009 04:13:21 +0000 Subject: 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 Signed-off-by: Wolfgang Grandegger Signed-off-by: David S. Miller --- include/linux/can/dev.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include') diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h index 1ed2a5cc03f..3db7767d2a1 100644 --- a/include/linux/can/dev.h +++ b/include/linux/can/dev.h @@ -51,6 +51,15 @@ struct can_priv { struct sk_buff **echo_skb; }; +/* + * get_can_dlc(value) - helper macro to cast a given data length code (dlc) + * to __u8 and ensure the dlc value to be max. 8 bytes. + * + * To be used in the CAN netdriver receive path to ensure conformance with + * ISO 11898-1 Chapter 8.4.2.3 (DLC field) + */ +#define get_can_dlc(i) (min_t(__u8, (i), 8)) + struct net_device *alloc_candev(int sizeof_priv, unsigned int echo_skb_max); void free_candev(struct net_device *dev); -- cgit v1.2.3