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

From: Mike Manning <[email-masked]>
Date: Mon, 18 Apr 2016 15:23:23 +0100

f1705ec197e7 "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
"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 either, 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