linux-kernel - [PATCH 3.16 147/202] net: fix IPv6 prefix route residue

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Message-ID: <lsq.1556377989.669742497@decadent.org.uk>
Date:   Sat, 27 Apr 2019 16:13:09 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Wenhao Zhang" <zhangwenhao8@...wei.com>,
        "Zhiqiang Liu" <liuzhiqiang26@...wei.com>
Subject: [PATCH 3.16 147/202] net: fix IPv6 prefix route residue

3.16.66-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Zhiqiang Liu <liuzhiqiang26@...wei.com>

commit e75913c93f7cd5f338ab373c34c93a655bd309cb upstream.

Follow those steps:
 # ip addr add 2001:123::1/32 dev eth0
 # ip addr add 2001:123:456::2/64 dev eth0
 # ip addr del 2001:123::1/32 dev eth0
 # ip addr del 2001:123:456::2/64 dev eth0
and then prefix route of 2001:123::1/32 will still exist.

This is because ipv6_prefix_equal in check_cleanup_prefix_route
func does not check whether two IPv6 addresses have the same
prefix length. If the prefix of one address starts with another
shorter address prefix, even though their prefix lengths are
different, the return value of ipv6_prefix_equal is true.

Here I add a check of whether two addresses have the same prefix
to decide whether their prefixes are equal.

Fixes: 5b84efecb7d9 ("ipv6 addrconf: don't cleanup prefix route for IFA_F_NOPREFIXROUTE")
Signed-off-by: Zhiqiang Liu <liuzhiqiang26@...wei.com>
Reported-by: Wenhao Zhang <zhangwenhao8@...wei.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/ipv6/addrconf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -943,7 +943,8 @@ check_cleanup_prefix_route(struct inet6_
 	list_for_each_entry(ifa, &idev->addr_list, if_list) {
 		if (ifa == ifp)
 			continue;
-		if (!ipv6_prefix_equal(&ifa->addr, &ifp->addr,
+		if (ifa->prefix_len != ifp->prefix_len ||
+		    !ipv6_prefix_equal(&ifa->addr, &ifp->addr,
 				       ifp->prefix_len))
 			continue;
 		if (ifa->flags & (IFA_F_PERMANENT | IFA_F_NOPREFIXROUTE))