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>

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 13a9098..fc59bc6 100644 (file)
--- 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 e24e669..2124c67 100644 (file)
--- 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 0a2a5ee..4e94057 100644 (file)
--- 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 2f0543f..f9bbbb4 100644 (file)
--- 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 d249874..a27f8aa 100644 (file)
--- 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 3fc737b..dcb75c0 100644 (file)
--- 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);