[PATCH mptcp-net 1/2] net: add sk_shutdown_timer_sync() helper

[Li Xiasong <xiasonglee@gmail.com>]

From: Li Xiasong <lixiasong1@huawei.com>

Add sk_shutdown_timer_sync(), a socket-timer helper wrapping
timer_shutdown_sync() with the same sk reference accounting used by
sk_stop_timer() and sk_stop_timer_sync().

When a pending timer is removed, the helper drops the corresponding sk
reference via __sock_put(). This provides a safe shutdown primitive for
final teardown paths where timer re-arming must be prevented.

Signed-off-by: Li Xiasong <lixiasong1@huawei.com>
---
 include/net/sock.h | 5 +++++
 net/core/sock.c    | 7 +++++++
 2 files changed, 12 insertions(+)

diff --git a/include/net/sock.h b/include/net/sock.h
index dccd3738c368..2de205e88271 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2496,6 +2496,11 @@ void sk_stop_timer(struct sock *sk, struct timer_list *timer);
 
 void sk_stop_timer_sync(struct sock *sk, struct timer_list *timer);
 
+/* Synchronously stop and permanently disable a socket timer.
+ * Drop @sk ref if a pending timer was removed.
+ */
+void sk_shutdown_timer_sync(struct sock *sk, struct timer_list *timer);
+
 int __sk_queue_drop_skb(struct sock *sk, struct sk_buff_head *sk_queue,
 			struct sk_buff *skb, unsigned int flags,
 			void (*destructor)(struct sock *sk,
diff --git a/net/core/sock.c b/net/core/sock.c
index b37b664b6eb9..4670bc3e6a41 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3696,6 +3696,13 @@ void sk_stop_timer_sync(struct sock *sk, struct timer_list *timer)
 }
 EXPORT_SYMBOL(sk_stop_timer_sync);
 
+void sk_shutdown_timer_sync(struct sock *sk, struct timer_list *timer)
+{
+	if (timer_shutdown_sync(timer))
+		__sock_put(sk);
+}
+EXPORT_SYMBOL(sk_shutdown_timer_sync);
+
 void sock_init_data_uid(struct socket *sock, struct sock *sk, kuid_t uid)
 {
 	sk_init_common(sk);
-- 
2.43.0