[IPV4]: Replace __in_dev_get with __in_dev_get_rcu/rtnl

The following patch renames __in_dev_get() to __in_dev_get_rtnl() and
introduces __in_dev_get_rcu() to cover the second case.

1) RCU with refcnt should use in_dev_get().
2) RCU without refcnt should use __in_dev_get_rcu().
3) All others must hold RTNL and use __in_dev_get_rtnl().

There is one exception in net/ipv4/route.c which is in fact a pre-existing
race condition.  I've marked it as such so that we remember to fix it.

This patch is based on suggestions and prior work by Suzanne Wood and
Paul McKenney.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 2 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 8549f26e2495..381dd6a6aebb 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2128,7 +2128,7 @@ int ip_route_input(struct sk_buff *skb, u32 daddr, u32 saddr,
                 struct in_device *in_dev;
 
                 rcu_read_lock();
-                if ((in_dev = __in_dev_get(dev)) != NULL) {
+                if ((in_dev = __in_dev_get_rcu(dev)) != NULL) {
                         int our = ip_check_mc(in_dev, daddr, saddr,
                                 skb->nh.iph->protocol);
                         if (our
@@ -2443,7 +2443,9 @@ static int ip_route_output_slow(struct rtable **rp, const struct flowi *oldflp)
                 err = -ENODEV;
                 if (dev_out == NULL)
                         goto out;
-                if (__in_dev_get(dev_out) == NULL) {
+
+                /* RACE: Check return value of inet_select_addr instead. */
+                if (__in_dev_get_rtnl(dev_out) == NULL) {
                         dev_put(dev_out);
                         goto out;       /* Wrong error code */
                 }