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@hartkopp.net>
Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/can/mcp251x.c b/drivers/net/can/mcp251x.c
index 78b1b69..9c5a153 100644
--- a/drivers/net/can/mcp251x.c
+++ b/drivers/net/can/mcp251x.c
@@ -403,9 +403,8 @@
for (i = 1; i < RXBDAT_OFF; i++)
buf[i] = mcp251x_read_reg(spi, RXBCTRL(buf_idx) + i);
- len = buf[RXBDLC_OFF] & RXBDLC_LEN_MASK;
- if (len > 8)
- len = 8;
+
+ len = get_can_dlc(buf[RXBDLC_OFF] & RXBDLC_LEN_MASK);
for (; i < (RXBDAT_OFF + len); i++)
buf[i] = mcp251x_read_reg(spi, RXBCTRL(buf_idx) + i);
} else {
@@ -455,13 +454,7 @@
(buf[RXBSIDL_OFF] >> RXBSIDL_SHIFT);
}
/* Data length */
- frame->can_dlc = buf[RXBDLC_OFF] & RXBDLC_LEN_MASK;
- if (frame->can_dlc > 8) {
- dev_warn(&spi->dev, "invalid frame recevied\n");
- priv->net->stats.rx_errors++;
- dev_kfree_skb(skb);
- return;
- }
+ frame->can_dlc = get_can_dlc(buf[RXBDLC_OFF] & RXBDLC_LEN_MASK);
memcpy(frame->data, buf + RXBDAT_OFF, frame->can_dlc);
priv->net->stats.rx_packets++;