Subject: [PATCH] tcp: Pass lockdep expression to RCU lists

From: Amol Grover <[email-masked]>
Date: Wed, 19 Feb 2020 15:35:46 +0530

tcp_cong_list is traversed using list_for_each_entry_rcu
outside an RCU read-side critical section but under the protection
of tcp_cong_list_lock.

Hence, add corresponding lockdep expression to silence false-positive
warnings, and harden RCU lists.

Signed-off-by: Amol Grover <[email-masked]>
---
 net/ipv4/tcp_cong.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 3737ec096650..8d4446ed309e 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -25,7 +25,8 @@ static struct tcp_congestion_ops *tcp_ca_find(const char *name)
 {
 	struct tcp_congestion_ops *e;
 
-	list_for_each_entry_rcu(e, &tcp_cong_list, list) {
+	list_for_each_entry_rcu(e, &tcp_cong_list, list,
+				lockdep_is_held(&tcp_cong_list_lock)) {
 		if (strcmp(e->name, name) == 0)
 			return e;
 	}
@@ -55,7 +56,8 @@ struct tcp_congestion_ops *tcp_ca_find_key(u32 key)
 {
 	struct tcp_congestion_ops *e;
 
-	list_for_each_entry_rcu(e, &tcp_cong_list, list) {
+	list_for_each_entry_rcu(e, &tcp_cong_list, list,
+				lockdep_is_held(&tcp_cong_list_lock)) {
 		if (e->key == key)
 			return e;
 	}
@@ -317,7 +319,8 @@ int tcp_set_allowed_congestion_control(char *val)
 	}
 
 	/* pass 2 clear old values */
-	list_for_each_entry_rcu(ca, &tcp_cong_list, list)
+	list_for_each_entry_rcu(ca, &tcp_cong_list, list,
+				lockdep_is_held(&tcp_cong_list_lock))
 		ca->flags &= ~TCP_CONG_NON_RESTRICTED;
 
 	/* pass 3 mark as allowed */
-- 
2.24.1