3 files changed, 20 insertions, 1 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 7c4167bc8266..b9586a137cad 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1488,6 +1488,11 @@ static inline void sk_wmem_free_skb(struct sock *sk, struct sk_buff *skb)
  */
 #define sock_owned_by_user(sk)  ((sk)->sk_lock.owned)
 
+static inline void sock_release_ownership(struct sock *sk)
+{
+        sk->sk_lock.owned = 0;
+}
+
 /*
  * Macro so as to not evaluate some arguments when
  * lockdep is not enabled.
diff --git a/net/core/sock.c b/net/core/sock.c
index 5b6a9431b017..c0fc6bdad1e3 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2357,10 +2357,13 @@ void release_sock(struct sock *sk)
         if (sk->sk_backlog.tail)
                 __release_sock(sk);
 
+        /* Warning : release_cb() might need to release sk ownership,
+         * ie call sock_release_ownership(sk) before us.
+         */
         if (sk->sk_prot->release_cb)
                 sk->sk_prot->release_cb(sk);
 
-        sk->sk_lock.owned = 0;
+        sock_release_ownership(sk);
         if (waitqueue_active(&sk->sk_lock.wq))
                 wake_up(&sk->sk_lock.wq);
         spin_unlock_bh(&sk->sk_lock.slock);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f0eb4e337ec8..17a11e65e57f 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -767,6 +767,17 @@ void tcp_release_cb(struct sock *sk)
         if (flags & (1UL << TCP_TSQ_DEFERRED))
                 tcp_tsq_handler(sk);
 
+        /* Here begins the tricky part :
+         * We are called from release_sock() with :
+         * 1) BH disabled
+         * 2) sk_lock.slock spinlock held
+         * 3) socket owned by us (sk->sk_lock.owned == 1)
+         *
+         * But following code is meant to be called from BH handlers,
+         * so we should keep BH disabled, but early release socket ownership
+         */
+        sock_release_ownership(sk);
+
         if (flags & (1UL << TCP_WRITE_TIMER_DEFERRED)) {
                 tcp_write_timer_handler(sk);
                 __sock_put(sk);