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can: Fix data length code handling in rx path

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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@hartkopp.net>
Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Oliver Hartkopp 2009-12-12 04:13:21 +00:00 • committed by David S. Miller
parent d90a909e1f
commit c7cd606f60
8 changed files with 26 additions and 25 deletions
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2
drivers/net/can/ti_hecc.c
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@ -552,7 +552,7 @@ static int ti_hecc_rx_pkt(struct ti_hecc_priv *priv, int mbxno)
data = hecc_read_mbx(priv, mbxno, HECC_CANMCF);
if (data & HECC_CANMCF_RTR)
cf->can_id |= CAN_RTR_FLAG;
cf->can_dlc = data & 0xF;
cf->can_dlc = get_can_dlc(data & 0xF);
data = hecc_read_mbx(priv, mbxno, HECC_CANMDL);
*(u32 *)(cf->data) = cpu_to_be32(data);
if (cf->can_dlc > 4) {