net/ipv6: Fix index counter for unicast addresses in in6_dump_addrs

From: David Ahern <[email protected]>

The loop wants to skip previously dumped addresses, so loops until current index >= saved index. If the message fills it wants to save the index for the next address to dump - ie., the one that did not fit in the current message.

Currently, it is incrementing the index counter before comparing to the saved index, and then the saved index is off by 1 - it assumes the current address is going to fit in the message.

Change the index handling to increment only after a succesful dump.

---
 net/ipv6/addrconf.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

index c63ccce6425f..4e81ff2f4588 100644
@@ -4928,8 +4928,8 @@ static int in6_dump_addrs(struct inet6_dev *idev, struct sk_buff *skb,
 
 		/* unicast address incl. temp addr */
 		list_for_each_entry(ifa, &idev->addr_list, if_list) {
-			if (++ip_idx < s_ip_idx)
-				continue;
+			if (ip_idx < s_ip_idx)
+				goto next;
 			err = inet6_fill_ifaddr(skb, ifa,
 						NETLINK_CB(cb->skb).portid,
 						cb->nlh->nlmsg_seq,

@@ -4938,6 +4938,8 @@ static int in6_dump_addrs(struct inet6_dev *idev, struct sk_buff *skb,
 			if (err < 0)
 				break;
 			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
+next:
+			ip_idx++;
 		}
 		break;
 	}

2.11.0

From: David Ahern <[email protected]>
Date: Fri, 19 Oct 2018 10:00:19 -0700

Applied and queued up for -stable, thanks David.