Subject: [PATCH] net: ipv6: Do not fix up linklocal and loopback addresses

From: Mike Manning <[email-masked]>
Date: Sat, 16 Apr 2016 04:13:21 +0100

f1705ec197e7 added the option to retain user configured addresses on an
admin down. A comment to one of the later revisions suggested using the
IFA_F_PERMANENT flag rather than adding a user_managed boolean to the
ifaddr struct. A side effect of this change is that link local and
loopback addresses are also retained which is not part of the objective
of f1705ec197e7. Add check so that these addresses are not fixed up,
given that a related fix 70af921db6f8 ensures that they are not kept in
the first place, otherwise this incorrect fixup triggers a crash in fib6.

Fixes: f1705ec197e7 ("net: ipv6: Make address flushing on ifdown optional")
Signed-off-by: Mike Manning <[email-masked]>
---
 net/ipv6/addrconf.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 23cec53..cba4e10 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3200,6 +3200,12 @@ static void l3mdev_check_host_rt(struct inet6_dev *idev,
 }
 #endif
 
+static bool addr_is_local(const struct in6_addr *addr)
+{
+	return ipv6_addr_type(addr) &
+		(IPV6_ADDR_LINKLOCAL | IPV6_ADDR_LOOPBACK);
+}
+
 static int fixup_permanent_addr(struct inet6_dev *idev,
 				struct inet6_ifaddr *ifp)
 {
@@ -3238,6 +3244,7 @@ static void addrconf_permanent_addr(struct net_device *dev)
 
 	list_for_each_entry_safe(ifp, tmp, &idev->addr_list, if_list) {
 		if ((ifp->flags & IFA_F_PERMANENT) &&
+		    !addr_is_local(&ifp->addr) &&
 		    fixup_permanent_addr(idev, ifp) < 0) {
 			write_unlock_bh(&idev->lock);
 			ipv6_del_addr(ifp);
@@ -3448,12 +3455,6 @@ static void addrconf_type_change(struct net_device *dev, unsigned long event)
 		ipv6_mc_unmap(idev);
 }
 
-static bool addr_is_local(const struct in6_addr *addr)
-{
-	return ipv6_addr_type(addr) &
-		(IPV6_ADDR_LINKLOCAL | IPV6_ADDR_LOOPBACK);
-}
-
 static int addrconf_ifdown(struct net_device *dev, int how)
 {
 	struct net *net = dev_net(dev);
-- 
1.7.10.4