[PATCH v2 2/2] can: dev: drop tx skb if in listen only mode

[Vincent Mailhol <mailhol.vincent@wanadoo.fr>]

Frames can be directly injected to a can driver via the packet
socket. By doing that, it is possible to reach the
net_device_ops::ndo_start_xmit function even if the driver is
configure in listen only mode.

Add a check in can_dropped_invalid_skb() and to discard the skb if
CAN_CTRLMODE_LISTENONLY is set.

Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
---
 drivers/net/can/dev/skb.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index 8b1991130de5..f7420fc43b99 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -5,6 +5,7 @@
  */
 
 #include <linux/can/dev.h>
+#include <linux/can/netlink.h>
 
 /* Local echo of CAN messages
  *
@@ -286,6 +287,7 @@ static bool can_skb_headroom_valid(struct net_device *dev, struct sk_buff *skb)
 bool can_dropped_invalid_skb(struct net_device *dev, struct sk_buff *skb)
 {
 	const struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
+	struct can_priv *priv = netdev_priv(dev);
 
 	if (skb->protocol == htons(ETH_P_CAN)) {
 		if (unlikely(skb->len != CAN_MTU ||
@@ -299,8 +301,13 @@ bool can_dropped_invalid_skb(struct net_device *dev, struct sk_buff *skb)
 		goto inval_skb;
 	}
 
-	if (!can_skb_headroom_valid(dev, skb))
+	if (!can_skb_headroom_valid(dev, skb)) {
+		goto inval_skb;
+	} else if (priv->ctrlmode & CAN_CTRLMODE_LISTENONLY) {
+		netdev_info_once(dev,
+				 "interface in listen only mode, dropping skb\n");
 		goto inval_skb;
+	}
 
 	return false;
 
-- 
2.35.1