IPv6: addrconf timer race

The Router Solicitation timer races with device state changes
because it doesn't lock the device. Use local variable to avoid
one repeated dereference.

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

1 files changed, 15 insertions, 13 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index e6cba9c45c6c..5f582f385abb 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2739,28 +2739,29 @@ static int addrconf_ifdown(struct net_device *dev, int how)
 static void addrconf_rs_timer(unsigned long data)
 {
         struct inet6_ifaddr *ifp = (struct inet6_ifaddr *) data;
+        struct inet6_dev *idev = ifp->idev;
 
-        if (ifp->idev->cnf.forwarding)
+        read_lock(&idev->lock);
+        if (idev->dead || !(idev->if_flags & IF_READY))
                 goto out;
 
-        if (ifp->idev->if_flags & IF_RA_RCVD) {
-                /*
-                 *      Announcement received after solicitation
-                 *      was sent
-                 */
+        if (idev->cnf.forwarding)
+                goto out;
+
+        /* Announcement received after solicitation was sent */
+        if (idev->if_flags & IF_RA_RCVD)
                 goto out;
-        }
 
         spin_lock(&ifp->lock);
-        if (ifp->probes++ < ifp->idev->cnf.rtr_solicits) {
+        if (ifp->probes++ < idev->cnf.rtr_solicits) {
                 /* The wait after the last probe can be shorter */
                 addrconf_mod_timer(ifp, AC_RS,
-                                   (ifp->probes == ifp->idev->cnf.rtr_solicits) ?
-                                   ifp->idev->cnf.rtr_solicit_delay :
-                                   ifp->idev->cnf.rtr_solicit_interval);
+                                   (ifp->probes == idev->cnf.rtr_solicits) ?
+                                   idev->cnf.rtr_solicit_delay :
+                                   idev->cnf.rtr_solicit_interval);
                 spin_unlock(&ifp->lock);
 
-                ndisc_send_rs(ifp->idev->dev, &ifp->addr, &in6addr_linklocal_allrouters);
+                ndisc_send_rs(idev->dev, &ifp->addr, &in6addr_linklocal_allrouters);
         } else {
                 spin_unlock(&ifp->lock);
                 /*
@@ -2768,10 +2769,11 @@ static void addrconf_rs_timer(unsigned long data)
                  * assumption any longer.
                  */
                 printk(KERN_DEBUG "%s: no IPv6 routers present\n",
-                       ifp->idev->dev->name);
+                       idev->dev->name);
         }
 
 out:
+        read_unlock(&idev->lock);
         in6_ifa_put(ifp);
 }