[PATCH v3 net-next 4/8] net: Add sk_clone().

sctp_accept() will use sk_clone_lock(), but it will be called
with the parent socket locked, and sctp_migrate() acquires the
child lock later.

Let's add no lock version of sk_clone_lock().

Note that lockdep complains if we simply use bh_lock_sock_nested().

Signed-off-by: Kuniyuki Iwashima <[email protected]>
---
v3: Check if (lock) for bh_unlock_sock(). (Xin Long)
---
 include/net/sock.h |  7 ++++++-
 net/core/sock.c    | 24 ++++++++++++++++--------
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 01ce231603db..c7e58b8e8a90 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1822,7 +1822,12 @@ struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
 void sk_free(struct sock *sk);
 void sk_net_refcnt_upgrade(struct sock *sk);
 void sk_destruct(struct sock *sk);
-struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority);
+struct sock *sk_clone(const struct sock *sk, const gfp_t priority, bool lock);
+
+static inline struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
+{
+	return sk_clone(sk, priority, true);
+}
 
 struct sk_buff *sock_wmalloc(struct sock *sk, unsigned long size, int force,
 			     gfp_t priority);
diff --git a/net/core/sock.c b/net/core/sock.c
index a99132cc0965..7a9bbc2afcf0 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2462,13 +2462,16 @@ static void sk_init_common(struct sock *sk)
 }
 
 /**
- *	sk_clone_lock - clone a socket, and lock its clone
- *	@sk: the socket to clone
- *	@priority: for allocation (%GFP_KERNEL, %GFP_ATOMIC, etc)
+ * sk_clone - clone a socket
+ * @sk: the socket to clone
+ * @priority: for allocation (%GFP_KERNEL, %GFP_ATOMIC, etc)
+ * @lock: if true, lock the cloned sk
  *
- *	Caller must unlock socket even in error path (bh_unlock_sock(newsk))
+ * If @lock is true, the clone is locked by bh_lock_sock(), and
+ * caller must unlock socket even in error path by bh_unlock_sock().
  */
-struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
+struct sock *sk_clone(const struct sock *sk, const gfp_t priority,
+		      bool lock)
 {
 	struct proto *prot = READ_ONCE(sk->sk_prot);
 	struct sk_filter *filter;
@@ -2497,9 +2500,13 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
 		__netns_tracker_alloc(sock_net(newsk), &newsk->ns_tracker,
 				      false, priority);
 	}
+
 	sk_node_init(&newsk->sk_node);
 	sock_lock_init(newsk);
-	bh_lock_sock(newsk);
+
+	if (lock)
+		bh_lock_sock(newsk);
+
 	newsk->sk_backlog.head	= newsk->sk_backlog.tail = NULL;
 	newsk->sk_backlog.len = 0;
 
@@ -2590,12 +2597,13 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
 	 * destructor and make plain sk_free()
 	 */
 	newsk->sk_destruct = NULL;
-	bh_unlock_sock(newsk);
+	if (lock)
+		bh_unlock_sock(newsk);
 	sk_free(newsk);
 	newsk = NULL;
 	goto out;
 }
-EXPORT_SYMBOL_GPL(sk_clone_lock);
+EXPORT_SYMBOL_GPL(sk_clone);
 
 static u32 sk_dst_gso_max_size(struct sock *sk, const struct net_device *dev)
 {
-- 
2.51.1.851.g4ebd6896fd-goog