netlink: Fix bugs in nlmsg_end() conversions.

Commit 053c095a ("netlink: make nlmsg_end() and genlmsg_end()
void") didn't catch all of the cases where callers were breaking out
on the return value being equal to zero, which they no longer should
when zero means success.

Fix all such cases.
Reported-by: NMarcel Holtmann <marcel@holtmann.org>
Reported-by: NScott Feldman <sfeldma@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/neighbour.c

@@ -2128,7 +2128,7 @@ static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 
 		if (neightbl_fill_info(skb, tbl, NETLINK_CB(cb->skb).portid,
 				       cb->nlh->nlmsg_seq, RTM_NEWNEIGHTBL,
-				       NLM_F_MULTI) <= 0)
+				       NLM_F_MULTI) < 0)
 			break;
 
 		nidx = 0;
@@ -2144,7 +2144,7 @@ static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 						     NETLINK_CB(cb->skb).portid,
 						     cb->nlh->nlmsg_seq,
 						     RTM_NEWNEIGHTBL,
-						     NLM_F_MULTI) <= 0)
+						     NLM_F_MULTI) < 0)
 				goto out;
 		next:
 			nidx++;
@@ -2274,7 +2274,7 @@ static int neigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
 			if (neigh_fill_info(skb, n, NETLINK_CB(cb->skb).portid,
 					    cb->nlh->nlmsg_seq,
 					    RTM_NEWNEIGH,
-					    NLM_F_MULTI) <= 0) {
+					    NLM_F_MULTI) < 0) {
 				rc = -1;
 				goto out;
 			}
@@ -2311,7 +2311,7 @@ static int pneigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
 			if (pneigh_fill_info(skb, n, NETLINK_CB(cb->skb).portid,
 					    cb->nlh->nlmsg_seq,
 					    RTM_NEWNEIGH,
-					    NLM_F_MULTI, tbl) <= 0) {
+					    NLM_F_MULTI, tbl) < 0) {
 				read_unlock_bh(&tbl->lock);
 				rc = -1;
 				goto out;

net/core/rtnetlink.c

@@ -1327,7 +1327,7 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
 			 */
 			WARN_ON((err == -EMSGSIZE) && (skb->len == 0));
 
-			if (err <= 0)
+			if (err < 0)
 				goto out;
 
 			nl_dump_check_consistent(cb, nlmsg_hdr(skb));

net/decnet/dn_route.c

@@ -1710,9 +1710,6 @@ static int dn_cache_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh)
 		rt->rt_flags |= RTCF_NOTIFY;
 
 	err = dn_rt_fill_info(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq, RTM_NEWROUTE, 0, 0);
-
-	if (err == 0)
-		goto out_free;
 	if (err < 0) {
 		err = -EMSGSIZE;
 		goto out_free;
@@ -1763,7 +1760,7 @@ int dn_cache_dump(struct sk_buff *skb, struct netlink_callback *cb)
 			skb_dst_set(skb, dst_clone(&rt->dst));
 			if (dn_rt_fill_info(skb, NETLINK_CB(cb->skb).portid,
 					cb->nlh->nlmsg_seq, RTM_NEWROUTE,
-					1, NLM_F_MULTI) <= 0) {
+					1, NLM_F_MULTI) < 0) {
 				skb_dst_drop(skb);
 				rcu_read_unlock_bh();
 				goto done;

net/ipv4/devinet.c

@@ -1883,7 +1883,7 @@ static int inet_netconf_dump_devconf(struct sk_buff *skb,
 						      cb->nlh->nlmsg_seq,
 						      RTM_NEWNETCONF,
 						      NLM_F_MULTI,
-						      -1) <= 0) {
+						      -1) < 0) {
 				rcu_read_unlock();
 				goto done;
 			}
@@ -1899,7 +1899,7 @@ static int inet_netconf_dump_devconf(struct sk_buff *skb,
 					      NETLINK_CB(cb->skb).portid,
 					      cb->nlh->nlmsg_seq,
 					      RTM_NEWNETCONF, NLM_F_MULTI,
-					      -1) <= 0)
+					      -1) < 0)
 			goto done;
 		else
 			h++;
@@ -1910,7 +1910,7 @@ static int inet_netconf_dump_devconf(struct sk_buff *skb,
 					      NETLINK_CB(cb->skb).portid,
 					      cb->nlh->nlmsg_seq,
 					      RTM_NEWNETCONF, NLM_F_MULTI,
-					      -1) <= 0)
+					      -1) < 0)
 			goto done;
 		else
 			h++;

net/ipv4/route.c

@@ -2483,7 +2483,7 @@ static int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh)
 	err = rt_fill_info(net, dst, src, &fl4, skb,
 			   NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
 			   RTM_NEWROUTE, 0, 0);
-	if (err <= 0)
+	if (err < 0)
 		goto errout_free;
 
 	err = rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);

net/ipv6/addrconf.c

@@ -4213,7 +4213,7 @@ static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
 				goto cont;
 
 			if (in6_dump_addrs(idev, skb, cb, type,
-					   s_ip_idx, &ip_idx) <= 0)
+					   s_ip_idx, &ip_idx) < 0)
 				goto done;
 cont:
 			idx++;