[PATCH][linux-bluetooth 1/3] 6lowpan: skb freed locally from lowpan_rcv

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Currently there are a number of error paths in the lowpan_rcv function that
free the skb before returning, this patch simplifies the receive path by
ensuring that the skb is only freed from this function.

Signed-off-by: Martin Townsend <martin.townsend@xxxxxxxxxx>
---
 include/net/6lowpan.h         |  2 +-
 net/6lowpan/iphc.c            | 27 +++++++++++++++------------
 net/bluetooth/6lowpan.c       | 12 ++++++++----
 net/ieee802154/6lowpan_rtnl.c | 12 ++++++------
 4 files changed, 30 insertions(+), 23 deletions(-)

diff --git a/include/net/6lowpan.h b/include/net/6lowpan.h
index d184df1..883e7a2 100644
--- a/include/net/6lowpan.h
+++ b/include/net/6lowpan.h
@@ -374,7 +374,7 @@ lowpan_uncompress_size(const struct sk_buff *skb, u16 *dgram_offset)
 
 typedef int (*skb_delivery_cb)(struct sk_buff *skb, struct net_device *dev);
 
-int lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
+int lowpan_process_data(struct sk_buff **skb_inout, struct net_device *dev,
 		const u8 *saddr, const u8 saddr_type, const u8 saddr_len,
 		const u8 *daddr, const u8 daddr_type, const u8 daddr_len,
 		u8 iphc0, u8 iphc1, skb_delivery_cb skb_deliver);
diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c
index 142eef5..eca24bf 100644
--- a/net/6lowpan/iphc.c
+++ b/net/6lowpan/iphc.c
@@ -179,11 +179,11 @@ static int skb_deliver(struct sk_buff *skb, struct ipv6hdr *hdr,
 
 	new = skb_copy_expand(skb, sizeof(struct ipv6hdr), skb_tailroom(skb),
 			      GFP_ATOMIC);
-	kfree_skb(skb);
-
 	if (!new)
 		return -ENOMEM;
 
+	kfree_skb(skb);
+
 	skb_push(new, sizeof(struct ipv6hdr));
 	skb_reset_network_header(new);
 	skb_copy_to_linear_data(new, hdr, sizeof(struct ipv6hdr));
@@ -196,6 +196,8 @@ static int skb_deliver(struct sk_buff *skb, struct ipv6hdr *hdr,
 		       new->data, new->len);
 
 	stat = deliver_skb(new, dev);
+	if (stat < 0)
+		stat = NET_RX_DROP;
 
 	kfree_skb(new);
 
@@ -332,7 +334,7 @@ err:
 /* TTL uncompression values */
 static const u8 lowpan_ttl_values[] = { 0, 1, 64, 255 };
 
-int lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
+int lowpan_process_data(struct sk_buff **skb_inout, struct net_device *dev,
 			const u8 *saddr, const u8 saddr_type, const u8 saddr_len,
 			const u8 *daddr, const u8 daddr_type, const u8 daddr_len,
 			u8 iphc0, u8 iphc1, skb_delivery_cb deliver_skb)
@@ -340,6 +342,8 @@ int lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
 	struct ipv6hdr hdr = {};
 	u8 tmp, num_context = 0;
 	int err;
+	int err_ret = -EINVAL;
+	struct sk_buff *skb = *skb_inout;
 
 	raw_dump_table(__func__, "raw skb data dump uncompressed",
 		       skb->data, skb->len);
@@ -460,7 +464,6 @@ int lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
 	/* UDP data uncompression */
 	if (iphc0 & LOWPAN_IPHC_NH_C) {
 		struct udphdr uh;
-		struct sk_buff *new;
 
 		if (uncompress_udp_header(skb, &uh))
 			goto drop;
@@ -468,14 +471,15 @@ int lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
 		/* replace the compressed UDP head by the uncompressed UDP
 		 * header
 		 */
-		new = skb_copy_expand(skb, sizeof(struct udphdr),
+		skb = skb_copy_expand(skb, sizeof(struct udphdr),
 				      skb_tailroom(skb), GFP_ATOMIC);
-		kfree_skb(skb);
-
-		if (!new)
-			return -ENOMEM;
+		if (!skb) {
+			err_ret = -ENOMEM;
+			goto drop;
+		}
 
-		skb = new;
+		kfree_skb(*skb_inout);
+		*skb_inout = skb;
 
 		skb_push(skb, sizeof(struct udphdr));
 		skb_reset_transport_header(skb);
@@ -502,8 +506,7 @@ int lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
 	return skb_deliver(skb, &hdr, dev, deliver_skb);
 
 drop:
-	kfree_skb(skb);
-	return -EINVAL;
+	return err_ret;
 }
 EXPORT_SYMBOL_GPL(lowpan_process_data);
 
diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
index 206b65c..f5f7ee0 100644
--- a/net/bluetooth/6lowpan.c
+++ b/net/bluetooth/6lowpan.c
@@ -215,7 +215,7 @@ static int give_skb_to_upper(struct sk_buff *skb, struct net_device *dev)
 	return ret;
 }
 
-static int process_data(struct sk_buff *skb, struct net_device *netdev,
+static int process_data(struct sk_buff **skb_inout, struct net_device *netdev,
 			struct l2cap_chan *chan)
 {
 	const u8 *saddr, *daddr;
@@ -223,6 +223,7 @@ static int process_data(struct sk_buff *skb, struct net_device *netdev,
 	struct lowpan_dev *dev;
 	struct lowpan_peer *peer;
 	unsigned long flags;
+	struct sk_buff *skb = *skb_inout;
 
 	dev = lowpan_dev(netdev);
 
@@ -245,13 +246,12 @@ static int process_data(struct sk_buff *skb, struct net_device *netdev,
 	if (lowpan_fetch_skb_u8(skb, &iphc1))
 		goto drop;
 
-	return lowpan_process_data(skb, netdev,
+	return lowpan_process_data(skb_inout, netdev,
 				   saddr, IEEE802154_ADDR_LONG, EUI64_ADDR_LEN,
 				   daddr, IEEE802154_ADDR_LONG, EUI64_ADDR_LEN,
 				   iphc0, iphc1, give_skb_to_upper);
 
 drop:
-	kfree_skb(skb);
 	return -EINVAL;
 }
 
@@ -300,7 +300,11 @@ static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
 			if (!local_skb)
 				goto drop;
 
-			ret = process_data(local_skb, dev, chan);
+			ret = process_data(&local_skb, dev, chan);
+			if (ret < 0) {
+				kfree_skb(local_skb);
+				goto drop;
+			}
 			if (ret != NET_RX_SUCCESS)
 				goto drop;
 
diff --git a/net/ieee802154/6lowpan_rtnl.c b/net/ieee802154/6lowpan_rtnl.c
index 6591d27..fdb6c10 100644
--- a/net/ieee802154/6lowpan_rtnl.c
+++ b/net/ieee802154/6lowpan_rtnl.c
@@ -167,11 +167,12 @@ static int lowpan_give_skb_to_devices(struct sk_buff *skb,
 	return stat;
 }
 
-static int process_data(struct sk_buff *skb, const struct ieee802154_hdr *hdr)
+static int process_data(struct sk_buff **skb_inout, const struct ieee802154_hdr *hdr)
 {
 	u8 iphc0, iphc1;
 	struct ieee802154_addr_sa sa, da;
 	void *sap, *dap;
+	struct sk_buff *skb = *skb_inout;
 
 	raw_dump_table(__func__, "raw skb data dump", skb->data, skb->len);
 	/* at least two bytes will be used for the encoding */
@@ -197,13 +198,12 @@ static int process_data(struct sk_buff *skb, const struct ieee802154_hdr *hdr)
 	else
 		dap = &da.hwaddr;
 
-	return lowpan_process_data(skb, skb->dev, sap, sa.addr_type,
+	return lowpan_process_data(skb_inout, skb->dev, sap, sa.addr_type,
 				   IEEE802154_ADDR_LEN, dap, da.addr_type,
 				   IEEE802154_ADDR_LEN, iphc0, iphc1,
 				   lowpan_give_skb_to_devices);
 
 drop:
-	kfree_skb(skb);
 	return -EINVAL;
 }
 
@@ -490,14 +490,14 @@ static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
 	} else {
 		switch (skb->data[0] & 0xe0) {
 		case LOWPAN_DISPATCH_IPHC:	/* ipv6 datagram */
-			ret = process_data(skb, &hdr);
+			ret = process_data(&skb, &hdr);
 			if (ret == NET_RX_DROP)
 				goto drop;
 			break;
 		case LOWPAN_DISPATCH_FRAG1:	/* first fragment header */
 			ret = lowpan_frag_rcv(skb, LOWPAN_DISPATCH_FRAG1);
 			if (ret == 1) {
-				ret = process_data(skb, &hdr);
+				ret = process_data(&skb, &hdr);
 				if (ret == NET_RX_DROP)
 					goto drop;
 			}
@@ -505,7 +505,7 @@ static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
 		case LOWPAN_DISPATCH_FRAGN:	/* next fragments headers */
 			ret = lowpan_frag_rcv(skb, LOWPAN_DISPATCH_FRAGN);
 			if (ret == 1) {
-				ret = process_data(skb, &hdr);
+				ret = process_data(&skb, &hdr);
 				if (ret == NET_RX_DROP)
 					goto drop;
 			}
-- 
1.9.1

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