1 files changed, 26 insertions, 10 deletions

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index ce23178..47fff52 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -239,7 +239,16 @@ int ip_cmsg_send(struct net *net, struct msghdr *msg, struct ipcm_cookie *ipc)
    sent to multicast group to reach destination designated router.
  */
 struct ip_ra_chain *ip_ra_chain;
-DEFINE_RWLOCK(ip_ra_lock);
+static DEFINE_SPINLOCK(ip_ra_lock);
+
+
+static void ip_ra_destroy_rcu(struct rcu_head *head)
+{
+	struct ip_ra_chain *ra = container_of(head, struct ip_ra_chain, rcu);
+
+	sock_put(ra->saved_sk);
+	kfree(ra);
+}
 
 int ip_ra_control(struct sock *sk, unsigned char on,
 		  void (*destructor)(struct sock *))
@@ -251,35 +260,42 @@ int ip_ra_control(struct sock *sk, unsigned char on,
 
 	new_ra = on ? kmalloc(sizeof(*new_ra), GFP_KERNEL) : NULL;
 
-	write_lock_bh(&ip_ra_lock);
+	spin_lock_bh(&ip_ra_lock);
 	for (rap = &ip_ra_chain; (ra = *rap) != NULL; rap = &ra->next) {
 		if (ra->sk == sk) {
 			if (on) {
-				write_unlock_bh(&ip_ra_lock);
+				spin_unlock_bh(&ip_ra_lock);
 				kfree(new_ra);
 				return -EADDRINUSE;
 			}
-			*rap = ra->next;
-			write_unlock_bh(&ip_ra_lock);
+			/* dont let ip_call_ra_chain() use sk again */
+			ra->sk = NULL;
+			rcu_assign_pointer(*rap, ra->next);
+			spin_unlock_bh(&ip_ra_lock);
 
 			if (ra->destructor)
 				ra->destructor(sk);
-			sock_put(sk);
-			kfree(ra);
+			/*
+			 * Delay sock_put(sk) and kfree(ra) after one rcu grace
+			 * period. This guarantee ip_call_ra_chain() dont need
+			 * to mess with socket refcounts.
+			 */
+			ra->saved_sk = sk;
+			call_rcu(&ra->rcu, ip_ra_destroy_rcu);
 			return 0;
 		}
 	}
 	if (new_ra == NULL) {
-		write_unlock_bh(&ip_ra_lock);
+		spin_unlock_bh(&ip_ra_lock);
 		return -ENOBUFS;
 	}
 	new_ra->sk = sk;
 	new_ra->destructor = destructor;
 
 	new_ra->next = ra;
-	*rap = new_ra;
+	rcu_assign_pointer(*rap, new_ra);
 	sock_hold(sk);
-	write_unlock_bh(&ip_ra_lock);
+	spin_unlock_bh(&ip_ra_lock);
 
 	return 0;
 }