can: Use WARN_ONCE() instead of BUG_ON() for sanity check in receive path

To ensure a proper handling of CAN frames transported in skbuffs some checks
need to be performed at receive time.

As stated by Michael Olbrich and Luotao Fu BUG_ON() might be to restrictive.
This is right as we can just drop the non conform skbuff and the Kernel can
continue working.

This patch replaces the BUG_ON() with a WARN_ONCE() so that the system remains
healthy but we made the problem visible (once).

Signed-off-by: Oliver Hartkopp <oliver@hartkopp.net>
Signed-off-by: Urs Thuermann <urs@isnogud.escape.de>
CC: Michael Olbrich <m.olbrich@pengutronix.de>
CC: Luotao Fu <l.fu@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 5 deletions

diff --git a/net/can/af_can.c b/net/can/af_can.c
index e733725b11d4..f9c027be78b2 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -651,12 +651,16 @@ static int can_rcv(struct sk_buff *skb, struct net_device *dev,
         struct can_frame *cf = (struct can_frame *)skb->data;
         int matches;
 
-        if (dev->type != ARPHRD_CAN || !net_eq(dev_net(dev), &init_net)) {
-                kfree_skb(skb);
-                return 0;
-        }
+        if (!net_eq(dev_net(dev), &init_net))
+                goto drop;
 
-        BUG_ON(skb->len != sizeof(struct can_frame) || cf->can_dlc > 8);
+        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))
+                goto drop;
 
         /* update statistics */
         can_stats.rx_frames++;
@@ -683,6 +687,10 @@ static int can_rcv(struct sk_buff *skb, struct net_device *dev,
         }
 
         return 0;
+
+drop:
+        kfree_skb(skb);
+        return 0;
 }
 
 /*