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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, David Ahern <dsahern@gmail.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.18 109/150] net/ipv6: Fix index counter for unicast addresses in in6_dump_addrs
Date:   Fri,  2 Nov 2018 19:34:31 +0100
Message-Id: <20181102182910.804827657@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Ahern <dsahern@gmail.com>

[ Upstream commit 4ba4c566ba8448a05e6257e0b98a21f1a0d55315 ]

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.

Fixes: 502a2ffd7376a ("ipv6: convert idev_list to list macros")
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv6/addrconf.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4930,8 +4930,8 @@ static int in6_dump_addrs(struct inet6_d
 
 		/* 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,
@@ -4940,6 +4940,8 @@ static int in6_dump_addrs(struct inet6_d
 			if (err < 0)
 				break;
 			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
+next:
+			ip_idx++;
 		}
 		break;
 	}