can: add destructor for self generated skbs

Self generated skbuffs in net/can/bcm.c are setting a skb->sk reference but
no explicit destructor which is enforced since Linux 3.11 with commit
376c7311bdb6 (net: add a temporary sanity check in skb_orphan()).

This patch adds some helper functions to make sure that a destructor is
properly defined when a sock reference is assigned to a CAN related skb.
To create an unshared skb owned by the original sock a common helper function
has been introduced to replace open coded functions to create CAN echo skbs.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Tested-by: Andre Naujoks <nautsch2@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 11 insertions, 31 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;
 }