From 51e13685bd93654e0e9b2559c8e103d6545ddf95 Mon Sep 17 00:00:00 2001
From: Jakub Kicinski <kuba@kernel.org>
Date: Wed, 9 Dec 2020 18:16:08 -0800
Subject: [PATCH] rtnetlink: RCU-annotate both dimensions of rtnl_msg_handlers

We use rcu_assign_pointer to assign both the table and the entries,
but the entries are not marked as __rcu. This generates sparse
warnings.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 net/core/rtnetlink.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 60917ff4a00b..bb0596c41b3e 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -139,7 +139,7 @@ bool lockdep_rtnl_is_held(void)
 EXPORT_SYMBOL(lockdep_rtnl_is_held);
 #endif /* #ifdef CONFIG_PROVE_LOCKING */
 
-static struct rtnl_link *__rcu *rtnl_msg_handlers[RTNL_FAMILY_MAX + 1];
+static struct rtnl_link __rcu *__rcu *rtnl_msg_handlers[RTNL_FAMILY_MAX + 1];
 
 static inline int rtm_msgindex(int msgtype)
 {
@@ -157,7 +157,7 @@ static inline int rtm_msgindex(int msgtype)
 
 static struct rtnl_link *rtnl_get_link(int protocol, int msgtype)
 {
-	struct rtnl_link **tab;
+	struct rtnl_link __rcu **tab;
 
 	if (protocol >= ARRAY_SIZE(rtnl_msg_handlers))
 		protocol = PF_UNSPEC;
@@ -166,7 +166,7 @@ static struct rtnl_link *rtnl_get_link(int protocol, int msgtype)
 	if (!tab)
 		tab = rcu_dereference_rtnl(rtnl_msg_handlers[PF_UNSPEC]);
 
-	return tab[msgtype];
+	return rcu_dereference_rtnl(tab[msgtype]);
 }
 
 static int rtnl_register_internal(struct module *owner,
@@ -183,7 +183,7 @@ static int rtnl_register_internal(struct module *owner,
 	msgindex = rtm_msgindex(msgtype);
 
 	rtnl_lock();
-	tab = rtnl_msg_handlers[protocol];
+	tab = rtnl_dereference(rtnl_msg_handlers[protocol]);
 	if (tab == NULL) {
 		tab = kcalloc(RTM_NR_MSGTYPES, sizeof(void *), GFP_KERNEL);
 		if (!tab)
@@ -286,7 +286,8 @@ void rtnl_register(int protocol, int msgtype,
  */
 int rtnl_unregister(int protocol, int msgtype)
 {
-	struct rtnl_link **tab, *link;
+	struct rtnl_link __rcu **tab;
+	struct rtnl_link *link;
 	int msgindex;
 
 	BUG_ON(protocol < 0 || protocol > RTNL_FAMILY_MAX);
@@ -299,7 +300,7 @@ int rtnl_unregister(int protocol, int msgtype)
 		return -ENOENT;
 	}
 
-	link = tab[msgindex];
+	link = rtnl_dereference(tab[msgindex]);
 	rcu_assign_pointer(tab[msgindex], NULL);
 	rtnl_unlock();
 
@@ -318,20 +319,21 @@ EXPORT_SYMBOL_GPL(rtnl_unregister);
  */
 void rtnl_unregister_all(int protocol)
 {
-	struct rtnl_link **tab, *link;
+	struct rtnl_link __rcu **tab;
+	struct rtnl_link *link;
 	int msgindex;
 
 	BUG_ON(protocol < 0 || protocol > RTNL_FAMILY_MAX);
 
 	rtnl_lock();
-	tab = rtnl_msg_handlers[protocol];
+	tab = rtnl_dereference(rtnl_msg_handlers[protocol]);
 	if (!tab) {
 		rtnl_unlock();
 		return;
 	}
 	RCU_INIT_POINTER(rtnl_msg_handlers[protocol], NULL);
 	for (msgindex = 0; msgindex < RTM_NR_MSGTYPES; msgindex++) {
-		link = tab[msgindex];
+		link = rtnl_dereference(tab[msgindex]);
 		if (!link)
 			continue;
 
@@ -3754,7 +3756,7 @@ static int rtnl_dump_all(struct sk_buff *skb, struct netlink_callback *cb)
 		s_idx = 1;
 
 	for (idx = 1; idx <= RTNL_FAMILY_MAX; idx++) {
-		struct rtnl_link **tab;
+		struct rtnl_link __rcu **tab;
 		struct rtnl_link *link;
 		rtnl_dumpit_func dumpit;
 
@@ -3768,7 +3770,7 @@ static int rtnl_dump_all(struct sk_buff *skb, struct netlink_callback *cb)
 		if (!tab)
 			continue;
 
-		link = tab[type];
+		link = rcu_dereference_rtnl(tab[type]);
 		if (!link)
 			continue;