[NETFILTER]: Fix incorrect use of skb_make_writable

http://bugzilla.kernel.org/show_bug.cgi?id=9920
The function skb_make_writable returns true or false.
Signed-off-by: NJoonwoo Park <joonwpark81@gmail.com>
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/bridge/netfilter/ebt_dnat.c

@@ -20,7 +20,7 @@ static int ebt_target_dnat(struct sk_buff *skb, unsigned int hooknr,
 {
 	const struct ebt_nat_info *info = data;
 
-	if (skb_make_writable(skb, 0))
+	if (!skb_make_writable(skb, 0))
 		return NF_DROP;
 
 	memcpy(eth_hdr(skb)->h_dest, info->mac, ETH_ALEN);

net/bridge/netfilter/ebt_redirect.c

@@ -21,7 +21,7 @@ static int ebt_target_redirect(struct sk_buff *skb, unsigned int hooknr,
 {
 	const struct ebt_redirect_info *info = data;
 
-	if (skb_make_writable(skb, 0))
+	if (!skb_make_writable(skb, 0))
 		return NF_DROP;
 
 	if (hooknr != NF_BR_BROUTING)

net/bridge/netfilter/ebt_snat.c

@@ -22,7 +22,7 @@ static int ebt_target_snat(struct sk_buff *skb, unsigned int hooknr,
 {
 	const struct ebt_nat_info *info = data;
 
-	if (skb_make_writable(skb, 0))
+	if (!skb_make_writable(skb, 0))
 		return NF_DROP;
 
 	memcpy(eth_hdr(skb)->h_source, info->mac, ETH_ALEN);

net/ipv4/netfilter/arpt_mangle.c

@@ -19,7 +19,7 @@ target(struct sk_buff *skb,
 	unsigned char *arpptr;
 	int pln, hln;
 
-	if (skb_make_writable(skb, skb->len))
+	if (!skb_make_writable(skb, skb->len))
 		return NF_DROP;
 
 	arp = arp_hdr(skb);