1 files changed, 20 insertions, 15 deletions

diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
index 77f396b679ce..5dce4291f0ed 100644
--- a/net/core/sock_reuseport.c
+++ b/net/core/sock_reuseport.c
@@ -93,6 +93,16 @@ static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse)
 	return more_reuse;
 }
 
+static void reuseport_free_rcu(struct rcu_head *head)
+{
+	struct sock_reuseport *reuse;
+
+	reuse = container_of(head, struct sock_reuseport, rcu);
+	if (reuse->prog)
+		bpf_prog_destroy(reuse->prog);
+	kfree(reuse);
+}
+
 /**
  *  reuseport_add_sock - Add a socket to the reuseport group of another.
  *  @sk:  New socket to add to the group.
@@ -101,7 +111,7 @@ static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse)
  */
 int reuseport_add_sock(struct sock *sk, struct sock *sk2)
 {
-	struct sock_reuseport *reuse;
+	struct sock_reuseport *old_reuse, *reuse;
 
 	if (!rcu_access_pointer(sk2->sk_reuseport_cb)) {
 		int err = reuseport_alloc(sk2);
@@ -112,10 +122,13 @@ int reuseport_add_sock(struct sock *sk, struct sock *sk2)
 
 	spin_lock_bh(&reuseport_lock);
 	reuse = rcu_dereference_protected(sk2->sk_reuseport_cb,
-					  lockdep_is_held(&reuseport_lock)),
-	WARN_ONCE(rcu_dereference_protected(sk->sk_reuseport_cb,
-					    lockdep_is_held(&reuseport_lock)),
-		  "socket already in reuseport group");
+					  lockdep_is_held(&reuseport_lock));
+	old_reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
+					     lockdep_is_held(&reuseport_lock));
+	if (old_reuse && old_reuse->num_socks != 1) {
+		spin_unlock_bh(&reuseport_lock);
+		return -EBUSY;
+	}
 
 	if (reuse->num_socks == reuse->max_socks) {
 		reuse = reuseport_grow(reuse);
@@ -133,19 +146,11 @@ int reuseport_add_sock(struct sock *sk, struct sock *sk2)
 
 	spin_unlock_bh(&reuseport_lock);
 
+	if (old_reuse)
+		call_rcu(&old_reuse->rcu, reuseport_free_rcu);
 	return 0;
 }
 
-static void reuseport_free_rcu(struct rcu_head *head)
-{
-	struct sock_reuseport *reuse;
-
-	reuse = container_of(head, struct sock_reuseport, rcu);
-	if (reuse->prog)
-		bpf_prog_destroy(reuse->prog);
-	kfree(reuse);
-}
-
 void reuseport_detach_sock(struct sock *sk)
 {
 	struct sock_reuseport *reuse;