From: Wen Gu <guwen@linux.alibaba.com>
Date: Fri, 22 Apr 2022 15:56:18 +0800
Subject: net/smc: Only save the original clcsock callback functions
Git-commit: 97b9af7a70936e331170c79040cc9bf20071b566
Patch-mainline: v5.18-rc5
References: git-fixes

Both listen and fallback process will save the current clcsock
callback functions and establish new ones. But if both of them
happen, the saved callback functions will be overwritten.

So this patch introduces some helpers to ensure that only save
the original callback functions of clcsock.

Fixes: 341adeec9ada ("net/smc: Forward wakeup to smc socket waitqueue after fallback")
Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
Acked-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 net/smc/af_smc.c    |   55 ++++++++++++++++++++++++++++++++++------------------
 net/smc/smc.h       |   29 +++++++++++++++++++++++++++
 net/smc/smc_close.c |    3 +-
 3 files changed, 67 insertions(+), 20 deletions(-)

--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -261,6 +261,7 @@ static struct sock *smc_sock_alloc(struc
 	sk->sk_prot->hash(sk);
 	sk_refcnt_debug_inc(sk);
 	mutex_init(&smc->clcsock_release_lock);
+	smc_init_saved_callbacks(smc);
 
 	return sk;
 }
@@ -670,9 +671,24 @@ static void smc_fback_error_report(struc
 	smc_fback_forward_wakeup(smc, clcsk, smc->clcsk_error_report);
 }
 
+static void smc_fback_replace_callbacks(struct smc_sock *smc)
+{
+	struct sock *clcsk = smc->clcsock->sk;
+
+	clcsk->sk_user_data = (void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY);
+
+	smc_clcsock_replace_cb(&clcsk->sk_state_change, smc_fback_state_change,
+			       &smc->clcsk_state_change);
+	smc_clcsock_replace_cb(&clcsk->sk_data_ready, smc_fback_data_ready,
+			       &smc->clcsk_data_ready);
+	smc_clcsock_replace_cb(&clcsk->sk_write_space, smc_fback_write_space,
+			       &smc->clcsk_write_space);
+	smc_clcsock_replace_cb(&clcsk->sk_error_report, smc_fback_error_report,
+			       &smc->clcsk_error_report);
+}
+
 static int smc_switch_to_fallback(struct smc_sock *smc, int reason_code)
 {
-	struct sock *clcsk;
 	int rc = 0;
 
 	mutex_lock(&smc->clcsock_release_lock);
@@ -680,10 +696,7 @@ static int smc_switch_to_fallback(struct
 		rc = -EBADF;
 		goto out;
 	}
-	clcsk = smc->clcsock->sk;
 
-	if (smc->use_fallback)
-		goto out;
 	smc->use_fallback = true;
 	smc->fallback_rsn = reason_code;
 	smc_stat_fallback(smc);
@@ -698,18 +711,7 @@ static int smc_switch_to_fallback(struct
 		 * in smc sk->sk_wq and they should be woken up
 		 * as clcsock's wait queue is woken up.
 		 */
-		smc->clcsk_state_change = clcsk->sk_state_change;
-		smc->clcsk_data_ready = clcsk->sk_data_ready;
-		smc->clcsk_write_space = clcsk->sk_write_space;
-		smc->clcsk_error_report = clcsk->sk_error_report;
-
-		clcsk->sk_state_change = smc_fback_state_change;
-		clcsk->sk_data_ready = smc_fback_data_ready;
-		clcsk->sk_write_space = smc_fback_write_space;
-		clcsk->sk_error_report = smc_fback_error_report;
-
-		smc->clcsock->sk->sk_user_data =
-			(void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY);
+		smc_fback_replace_callbacks(smc);
 	}
 out:
 	mutex_unlock(&smc->clcsock_release_lock);
@@ -1474,6 +1476,19 @@ static int smc_clcsock_accept(struct smc
 	 * function; switch it back to the original sk_data_ready function
 	 */
 	new_clcsock->sk->sk_data_ready = lsmc->clcsk_data_ready;
+
+	/* if new clcsock has also inherited the fallback-specific callback
+	 * functions, switch them back to the original ones.
+	 */
+	if (lsmc->use_fallback) {
+		if (lsmc->clcsk_state_change)
+			new_clcsock->sk->sk_state_change = lsmc->clcsk_state_change;
+		if (lsmc->clcsk_write_space)
+			new_clcsock->sk->sk_write_space = lsmc->clcsk_write_space;
+		if (lsmc->clcsk_error_report)
+			new_clcsock->sk->sk_error_report = lsmc->clcsk_error_report;
+	}
+
 	(*new_smc)->clcsock = new_clcsock;
 out:
 	return rc;
@@ -2269,13 +2284,15 @@ static int smc_listen(struct socket *soc
 	/* save original sk_data_ready function and establish
 	 * smc-specific sk_data_ready function
 	 */
-	smc->clcsk_data_ready = smc->clcsock->sk->sk_data_ready;
-	smc->clcsock->sk->sk_data_ready = smc_clcsock_data_ready;
 	smc->clcsock->sk->sk_user_data =
 		(void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY);
+	smc_clcsock_replace_cb(&smc->clcsock->sk->sk_data_ready,
+			       smc_clcsock_data_ready, &smc->clcsk_data_ready);
 	rc = kernel_listen(smc->clcsock, backlog);
 	if (rc) {
-		smc->clcsock->sk->sk_data_ready = smc->clcsk_data_ready;
+		smc_clcsock_restore_cb(&smc->clcsock->sk->sk_data_ready,
+				       &smc->clcsk_data_ready);
+		smc->clcsock->sk->sk_user_data = NULL;
 		goto out;
 	}
 	sk->sk_max_ack_backlog = backlog;
--- a/net/smc/smc.h
+++ b/net/smc/smc.h
@@ -275,12 +275,41 @@ static inline struct smc_sock *smc_sk(co
 	return (struct smc_sock *)sk;
 }
 
+static inline void smc_init_saved_callbacks(struct smc_sock *smc)
+{
+	smc->clcsk_state_change	= NULL;
+	smc->clcsk_data_ready	= NULL;
+	smc->clcsk_write_space	= NULL;
+	smc->clcsk_error_report	= NULL;
+}
+
 static inline struct smc_sock *smc_clcsock_user_data(struct sock *clcsk)
 {
 	return (struct smc_sock *)
 	       ((uintptr_t)clcsk->sk_user_data & ~SK_USER_DATA_NOCOPY);
 }
 
+/* save target_cb in saved_cb, and replace target_cb with new_cb */
+static inline void smc_clcsock_replace_cb(void (**target_cb)(struct sock *),
+					  void (*new_cb)(struct sock *),
+					  void (**saved_cb)(struct sock *))
+{
+	/* only save once */
+	if (!*saved_cb)
+		*saved_cb = *target_cb;
+	*target_cb = new_cb;
+}
+
+/* restore target_cb to saved_cb, and reset saved_cb to NULL */
+static inline void smc_clcsock_restore_cb(void (**target_cb)(struct sock *),
+					  void (**saved_cb)(struct sock *))
+{
+	if (!*saved_cb)
+		return;
+	*target_cb = *saved_cb;
+	*saved_cb = NULL;
+}
+
 extern struct workqueue_struct	*smc_hs_wq;	/* wq for handshake work */
 extern struct workqueue_struct	*smc_close_wq;	/* wq for close work */
 
--- a/net/smc/smc_close.c
+++ b/net/smc/smc_close.c
@@ -211,7 +211,8 @@ again:
 		sk->sk_state = SMC_CLOSED;
 		sk->sk_state_change(sk); /* wake up accept */
 		if (smc->clcsock && smc->clcsock->sk) {
-			smc->clcsock->sk->sk_data_ready = smc->clcsk_data_ready;
+			smc_clcsock_restore_cb(&smc->clcsock->sk->sk_data_ready,
+					       &smc->clcsk_data_ready);
 			smc->clcsock->sk->sk_user_data = NULL;
 			rc = kernel_sock_shutdown(smc->clcsock, SHUT_RDWR);
 		}