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

From: Mike Manning <[email-masked]>
Date: Mon, 18 Apr 2016 16:28:43 +0100

f1705ec197e7 ("net: ipv6: Make address flushing on ifdown optional") 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 were also retained which
was not part of the objective of the original changes. The fix 70af921db6f8
("net: ipv6: Do not keep linklocal and loopback addresses") ensures that these
are no longer kept. Similarly, the present fix ensures that these addresses
are not fixed up, otherwise the 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