6 files changed, 53 insertions, 34 deletions

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 13a909822e25..fc59bc6f040b 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -323,19 +323,10 @@ void can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
         }
 
         if (!priv->echo_skb[idx]) {
-                struct sock *srcsk = skb->sk;
 
-                if (atomic_read(&skb->users) != 1) {
-                        struct sk_buff *old_skb = skb;
-
-                        skb = skb_clone(old_skb, GFP_ATOMIC);
-                        kfree_skb(old_skb);
-                        if (!skb)
-                                return;
-                } else
-                        skb_orphan(skb);
-
-                skb->sk = srcsk;
+                skb = can_create_echo_skb(skb);
+                if (!skb)
+                        return;
 
                 /* make settings for echo to reduce code in irq context */
                 skb->protocol = htons(ETH_P_CAN);
diff --git a/drivers/net/can/janz-ican3.c b/drivers/net/can/janz-ican3.c
index e24e6690d672..2124c6790687 100644
--- a/drivers/net/can/janz-ican3.c
+++ b/drivers/net/can/janz-ican3.c
@@ -18,6 +18,7 @@
 #include <linux/netdevice.h>
 #include <linux/can.h>
 #include <linux/can/dev.h>
+#include <linux/can/skb.h>
 #include <linux/can/error.h>
 
 #include <linux/mfd/janz.h>
@@ -1133,20 +1134,9 @@ static void ican3_handle_message(struct ican3_dev *mod, struct ican3_msg *msg)
  */
 static void ican3_put_echo_skb(struct ican3_dev *mod, struct sk_buff *skb)
 {
-        struct sock *srcsk = skb->sk;
-
-        if (atomic_read(&skb->users) != 1) {
-                struct sk_buff *old_skb = skb;
-
-                skb = skb_clone(old_skb, GFP_ATOMIC);
-                kfree_skb(old_skb);
-                if (!skb)
-                        return;
-        } else {
-                skb_orphan(skb);
-        }
-
-        skb->sk = srcsk;
+        skb = can_create_echo_skb(skb);
+        if (!skb)
+                return;
 
         /* save this skb for tx interrupt echo handling */
         skb_queue_tail(&mod->echoq, skb);
diff --git a/drivers/net/can/vcan.c b/drivers/net/can/vcan.c
index 0a2a5ee79a17..4e94057ef5cf 100644
--- a/drivers/net/can/vcan.c
+++ b/drivers/net/can/vcan.c
@@ -46,6 +46,7 @@
 #include <linux/if_ether.h>
 #include <linux/can.h>
 #include <linux/can/dev.h>
+#include <linux/can/skb.h>
 #include <linux/slab.h>
 #include <net/rtnetlink.h>
 
@@ -109,25 +110,23 @@ static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
                         stats->rx_packets++;
                         stats->rx_bytes += cfd->len;
                 }
-                kfree_skb(skb);
+                consume_skb(skb);
                 return NETDEV_TX_OK;
         }
 
         /* perform standard echo handling for CAN network interfaces */
 
         if (loop) {
-                struct sock *srcsk = skb->sk;
 
-                skb = skb_share_check(skb, GFP_ATOMIC);
+                skb = can_create_echo_skb(skb);
                 if (!skb)
                         return NETDEV_TX_OK;
 
                 /* receive with packet counting */
-                skb->sk = srcsk;
                 vcan_rx(skb, dev);
         } else {
                 /* no looped packets => no counting */
-                kfree_skb(skb);
+                consume_skb(skb);
         }
         return NETDEV_TX_OK;
 }
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index 2f0543f7510c..f9bbbb472663 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -11,7 +11,9 @@
 #define CAN_SKB_H
 
 #include <linux/types.h>
+#include <linux/skbuff.h>
 #include <linux/can.h>
+#include <net/sock.h>
 
 /*
  * The struct can_skb_priv is used to transport additional information along
@@ -42,4 +44,40 @@ static inline void can_skb_reserve(struct sk_buff *skb)
         skb_reserve(skb, sizeof(struct can_skb_priv));
 }
 
+static inline void can_skb_destructor(struct sk_buff *skb)
+{
+        sock_put(skb->sk);
+}
+
+static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk)
+{
+        if (sk) {
+                sock_hold(sk);
+                skb->destructor = can_skb_destructor;
+                skb->sk = sk;
+        }
+}
+
+/*
+ * returns an unshared skb owned by the original sock to be echo'ed back
+ */
+static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb)
+{
+        if (skb_shared(skb)) {
+                struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
+
+                if (likely(nskb)) {
+                        can_skb_set_owner(nskb, skb->sk);
+                        consume_skb(skb);
+                        return nskb;
+                } else {
+                        kfree_skb(skb);
+                        return NULL;
+                }
+        }
+
+        /* we can assume to have an unshared skb with proper owner */
+        return skb;
+}
+
 #endif /* CAN_SKB_H */
diff --git a/net/can/af_can.c b/net/can/af_can.c
index d249874a366d..a27f8aad9e99 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -57,6 +57,7 @@
 #include <linux/skbuff.h>
 #include <linux/can.h>
 #include <linux/can/core.h>
+#include <linux/can/skb.h>
 #include <linux/ratelimit.h>
 #include <net/net_namespace.h>
 #include <net/sock.h>
@@ -290,7 +291,7 @@ int can_send(struct sk_buff *skb, int loop)
                                 return -ENOMEM;
                         }
 
-                        newskb->sk = skb->sk;
+                        can_skb_set_owner(newskb, skb->sk);
                         newskb->ip_summed = CHECKSUM_UNNECESSARY;
                         newskb->pkt_type = PACKET_BROADCAST;
                 }
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 3fc737b214c7..dcb75c0e66c1 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -268,7 +268,7 @@ static void bcm_can_tx(struct bcm_op *op)
 
         /* send with loopback */
         skb->dev = dev;
-        skb->sk = op->sk;
+        can_skb_set_owner(skb, op->sk);
         can_send(skb, 1);
 
         /* update statistics */
@@ -1223,7 +1223,7 @@ static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk)
 
         can_skb_prv(skb)->ifindex = dev->ifindex;
         skb->dev = dev;
-        skb->sk  = sk;
+        can_skb_set_owner(skb, sk);
         err = can_send(skb, 1); /* send with loopback */
         dev_put(dev);