can: omit unneeded skb_clone() calls

The AF_CAN core delivered always cloned sk_buffs to the AF_CAN
protocols, although this was _only_ needed by the can-raw protocol.
With this (additionally documented) change, the AF_CAN core calls the
callback functions of the registered AF_CAN protocols with the original
(uncloned) sk_buff pointer and let's the can-raw protocol do the
skb_clone() itself which omits all unneeded skb_clone() calls for other
AF_CAN protocols.

Signed-off-by: Oliver Hartkopp <oliver@hartkopp.net>
Signed-off-by: Urs Thuermann <urs.thuermann@volkswagen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 7 deletions

diff --git a/net/can/af_can.c b/net/can/af_can.c
index 3dadb338addd..fa417ca6cbe6 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -414,6 +414,12 @@ static struct hlist_head *find_rcv_list(canid_t *can_id, canid_t *mask,
  *  The filter can be inverted (CAN_INV_FILTER bit set in can_id) or it can
  *  filter for error frames (CAN_ERR_FLAG bit set in mask).
  *
+ *  The provided pointer to the sk_buff is guaranteed to be valid as long as
+ *  the callback function is running. The callback function must *not* free
+ *  the given sk_buff while processing it's task. When the given sk_buff is
+ *  needed after the end of the callback function it must be cloned inside
+ *  the callback function with skb_clone().
+ *
  * Return:
  *  0 on success
  *  -ENOMEM on missing cache mem to create subscription entry
@@ -569,13 +575,8 @@ EXPORT_SYMBOL(can_rx_unregister);
 
 static inline void deliver(struct sk_buff *skb, struct receiver *r)
 {
-	struct sk_buff *clone = skb_clone(skb, GFP_ATOMIC);
-
-	if (clone) {
-		clone->sk = skb->sk;
-		r->func(clone, r->data);
-		r->matches++;
-	}
+	r->func(skb, r->data);
+	r->matches++;
 }
 
 static int can_rcv_filter(struct dev_rcv_lists *d, struct sk_buff *skb)