IPv6: fix race between cleanup and add/delete address

This solves a potential race problem during the cleanup process.
The issue is that addrconf_ifdown() needs to traverse address list,
but then drop lock to call the notifier. The version in -next
could get confused if add/delete happened during this window.
Original code (2.6.32 and earlier) was okay because all addresses
were always deleted.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 5 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 7a4bf7671285..6cf3ee14ace3 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2615,7 +2615,7 @@ static void addrconf_bonding_change(struct net_device *dev, unsigned long event)
 static int addrconf_ifdown(struct net_device *dev, int how)
 {
         struct inet6_dev *idev;
-        struct inet6_ifaddr *ifa, **bifa;
+        struct inet6_ifaddr *ifa, *keep_list, **bifa;
         struct net *net = dev_net(dev);
         int i;
 
@@ -2689,8 +2689,12 @@ static int addrconf_ifdown(struct net_device *dev, int how)
                 write_lock_bh(&idev->lock);
         }
 #endif
-        bifa = &idev->addr_list;
-        while ((ifa = *bifa) != NULL) {
+        keep_list = NULL;
+        bifa = &keep_list;
+        while ((ifa = idev->addr_list) != NULL) {
+                idev->addr_list = ifa->if_next;
+                ifa->if_next = NULL;
+
                 addrconf_del_timer(ifa);
 
                 /* If just doing link down, and address is permanent
@@ -2698,6 +2702,9 @@ static int addrconf_ifdown(struct net_device *dev, int how)
                 if (how == 0 &&
                     (ifa->flags&IFA_F_PERMANENT) &&
                     !(ipv6_addr_type(&ifa->addr) & IPV6_ADDR_LINKLOCAL)) {
+
+                        /* Move to holding list */
+                        *bifa = ifa;
                         bifa = &ifa->if_next;
 
                         /* If not doing DAD on this address, just keep it. */
@@ -2714,8 +2721,6 @@ static int addrconf_ifdown(struct net_device *dev, int how)
                         ifa->flags |= IFA_F_TENTATIVE;
                         in6_ifa_hold(ifa);
                 } else {
-                        *bifa = ifa->if_next;
-                        ifa->if_next = NULL;
                         ifa->dead = 1;
                 }
                 write_unlock_bh(&idev->lock);
@@ -2726,6 +2731,9 @@ static int addrconf_ifdown(struct net_device *dev, int how)
 
                 write_lock_bh(&idev->lock);
         }
+
+        idev->addr_list = keep_list;
+
         write_unlock_bh(&idev->lock);
 
         /* Step 5: Discard multicast list */