linux-kernel - [PATCH] tcp: ipv4: Pass lockdep expression to RCU lists

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Date:   Fri, 21 Feb 2020 20:51:54 +0530
From:   Amol Grover <frextrite@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Joel Fernandes <joel@...lfernandes.org>,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Amol Grover <frextrite@...il.com>
Subject: [PATCH] tcp: ipv4: Pass lockdep expression to RCU lists

md5sig->head maybe traversed using hlist_for_each_entry_rcu
outside an RCU read-side critical section but under the protection
of socket lock.

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

Signed-off-by: Amol Grover <frextrite@...il.com>
---
 net/ipv4/tcp_ipv4.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 1c7326e04f9b..6519429f32cd 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1000,7 +1000,8 @@ struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk,
 	if (!md5sig)
 		return NULL;
 
-	hlist_for_each_entry_rcu(key, &md5sig->head, node) {
+	hlist_for_each_entry_rcu(key, &md5sig->head, node,
+				 lockdep_sock_is_held(sk)) {
 		if (key->family != family)
 			continue;
 
@@ -1043,7 +1044,8 @@ static struct tcp_md5sig_key *tcp_md5_do_lookup_exact(const struct sock *sk,
 	if (family == AF_INET6)
 		size = sizeof(struct in6_addr);
 #endif
-	hlist_for_each_entry_rcu(key, &md5sig->head, node) {
+	hlist_for_each_entry_rcu(key, &md5sig->head, node,
+				 lockdep_sock_is_held(sk)) {
 		if (key->family != family)
 			continue;
 		if (!memcmp(&key->addr, addr, size) &&
-- 
2.24.1