[PATCH 3.2 110/140] can: af_can: can_rcv(): replace WARN_ONCE by pr_warn_once

[Ben Hutchings]

3.2.100-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>

commit 8cb68751c115d176ec851ca56ecfbb411568c9e8 upstream.

If an invalid CAN frame is received, from a driver or from a tun
interface, a Kernel warning is generated.

This patch replaces the WARN_ONCE by a simple pr_warn_once, so that a
kernel, bootet with panic_on_warn, does not panic. A printk seems to be
more appropriate here.

Reported-by: syzbot+4386709c0c1284dca827@xxxxxxxxxxxxxxxxxxxxxxxxx
Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Acked-by: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
[bwh: Backported to 3.2:
 - Keep using the 'drop' label, as it has another user
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -653,13 +653,13 @@ static int can_rcv(struct sk_buff *skb,
 	if (!net_eq(dev_net(dev), &init_net))
 		goto drop;
 
-	if (WARN_ONCE(dev->type != ARPHRD_CAN ||
-		      skb->len != sizeof(struct can_frame) ||
-		      cf->can_dlc > 8,
-		      "PF_CAN: dropped non conform skbuf: "
-		      "dev type %d, len %d, can_dlc %d\n",
-		      dev->type, skb->len, cf->can_dlc))
+	if (unlikely(dev->type != ARPHRD_CAN ||
+		     skb->len != sizeof(struct can_frame) ||
+		     cf->can_dlc > 8)) {
+		pr_warn_once("PF_CAN: dropped non conform CAN skbuf: dev type %d, len %d, can_dlc %d\n",
+			     dev->type, skb->len, cf->can_dlc);
 		goto drop;
+	}
 
 	/* update statistics */
 	can_stats.rx_frames++;