inet: RCU changes in inetdev_by_index()

Convert inetdev_by_index() to not increment in_dev refcount.

Callers hold RCU or RTNL, and should not decrement in_dev refcount.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 16 insertions, 22 deletions

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index c2ff48fa18c7..dc94b0316b78 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -403,6 +403,9 @@ static int inet_set_ifa(struct net_device *dev, struct in_ifaddr *ifa)
         return inet_insert_ifa(ifa);
 }
 
+/* Caller must hold RCU or RTNL :
+ * We dont take a reference on found in_device
+ */
 struct in_device *inetdev_by_index(struct net *net, int ifindex)
 {
         struct net_device *dev;
@@ -411,7 +414,7 @@ struct in_device *inetdev_by_index(struct net *net, int ifindex)
         rcu_read_lock();
         dev = dev_get_by_index_rcu(net, ifindex);
         if (dev)
-                in_dev = in_dev_get(dev);
+                in_dev = rcu_dereference_rtnl(dev->ip_ptr);
         rcu_read_unlock();
         return in_dev;
 }
@@ -453,8 +456,6 @@ static int inet_rtm_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg
                 goto errout;
         }
 
-        __in_dev_put(in_dev);
-
         for (ifap = &in_dev->ifa_list; (ifa = *ifap) != NULL;
              ifap = &ifa->ifa_next) {
                 if (tb[IFA_LOCAL] &&
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 0f80dfc2f7fb..6734c9cab248 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -590,32 +590,29 @@ static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
                 if (!dev)
                         goto out;
                 dev_hold(dev);
-                err = -ENETDOWN;
-                if (!(dev->flags & IFF_UP))
-                        goto out;
-                err = 0;
-out:
-                rcu_read_unlock();
-                return err;
+                err = (dev->flags & IFF_UP) ? 0 : -ENETDOWN;
         } else {
                 struct in_device *in_dev;
 
                 if (nh->nh_flags & (RTNH_F_PERVASIVE | RTNH_F_ONLINK))
                         return -EINVAL;
 
+                rcu_read_lock();
+                err = -ENODEV;
                 in_dev = inetdev_by_index(net, nh->nh_oif);
                 if (in_dev == NULL)
-                        return -ENODEV;
-                if (!(in_dev->dev->flags & IFF_UP)) {
-                        in_dev_put(in_dev);
-                        return -ENETDOWN;
-                }
+                        goto out;
+                err = -ENETDOWN;
+                if (!(in_dev->dev->flags & IFF_UP))
+                        goto out;
                 nh->nh_dev = in_dev->dev;
                 dev_hold(nh->nh_dev);
                 nh->nh_scope = RT_SCOPE_HOST;
-                in_dev_put(in_dev);
+                err = 0;
         }
-        return 0;
+out:
+        rcu_read_unlock();
+        return err;
 }
 
 static inline unsigned int fib_laddr_hashfn(__be32 val)
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index a525328ec372..c8877c6c7216 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -1429,8 +1429,6 @@ static struct in_device *ip_mc_find_dev(struct net *net, struct ip_mreqn *imr)
 
         if (imr->imr_ifindex) {
                 idev = inetdev_by_index(net, imr->imr_ifindex);
-                if (idev)
-                        __in_dev_put(idev);
                 return idev;
         }
         if (imr->imr_address.s_addr) {
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 9d421f4cf3ef..d0ffcbe369b7 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1245,10 +1245,8 @@ static int ipgre_close(struct net_device *dev)
         if (ipv4_is_multicast(t->parms.iph.daddr) && t->mlink) {
                 struct in_device *in_dev;
                 in_dev = inetdev_by_index(dev_net(dev), t->mlink);
-                if (in_dev) {
+                if (in_dev)
                         ip_mc_dec_group(in_dev, t->parms.iph.daddr);
-                        in_dev_put(in_dev);
-                }
         }
         return 0;
 }