netdev - [PATCH net-next 08/10] l2tp: use add READ_ONCE() to fetch sk->sk_bound_dev

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Date:   Wed, 11 May 2022 16:37:55 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 08/10] l2tp: use add READ_ONCE() to fetch sk->sk_bound_dev_if

From: Eric Dumazet <edumazet@...gle.com>

Use READ_ONCE() in paths not holding the socket lock.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/l2tp/l2tp_ip.c  | 4 +++-
 net/l2tp/l2tp_ip6.c | 8 +++++---
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index 6af09e188e52cfd84defb42ad34aea25f66f1e25..4db5a554bdbd9e80eb697a88cb7208e15d7931bc 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -50,11 +50,13 @@ static struct sock *__l2tp_ip_bind_lookup(const struct net *net, __be32 laddr,
 	sk_for_each_bound(sk, &l2tp_ip_bind_table) {
 		const struct l2tp_ip_sock *l2tp = l2tp_ip_sk(sk);
 		const struct inet_sock *inet = inet_sk(sk);
+		int bound_dev_if;
 
 		if (!net_eq(sock_net(sk), net))
 			continue;
 
-		if (sk->sk_bound_dev_if && dif && sk->sk_bound_dev_if != dif)
+		bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
+		if (bound_dev_if && dif && bound_dev_if != dif)
 			continue;
 
 		if (inet->inet_rcv_saddr && laddr &&
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
index 217c7192691e160e9727afd78126006aba3736b4..c6ff8bf9b55f916e80380bb2e4ea81b11e544a32 100644
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -62,11 +62,13 @@ static struct sock *__l2tp_ip6_bind_lookup(const struct net *net,
 		const struct in6_addr *sk_laddr = inet6_rcv_saddr(sk);
 		const struct in6_addr *sk_raddr = &sk->sk_v6_daddr;
 		const struct l2tp_ip6_sock *l2tp = l2tp_ip6_sk(sk);
+		int bound_dev_if;
 
 		if (!net_eq(sock_net(sk), net))
 			continue;
 
-		if (sk->sk_bound_dev_if && dif && sk->sk_bound_dev_if != dif)
+		bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
+		if (bound_dev_if && dif && bound_dev_if != dif)
 			continue;
 
 		if (sk_laddr && !ipv6_addr_any(sk_laddr) &&
@@ -445,7 +447,7 @@ static int l2tp_ip6_getname(struct socket *sock, struct sockaddr *uaddr,
 		lsa->l2tp_conn_id = lsk->conn_id;
 	}
 	if (ipv6_addr_type(&lsa->l2tp_addr) & IPV6_ADDR_LINKLOCAL)
-		lsa->l2tp_scope_id = sk->sk_bound_dev_if;
+		lsa->l2tp_scope_id = READ_ONCE(sk->sk_bound_dev_if);
 	return sizeof(*lsa);
 }
 
@@ -560,7 +562,7 @@ static int l2tp_ip6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	}
 
 	if (fl6.flowi6_oif == 0)
-		fl6.flowi6_oif = sk->sk_bound_dev_if;
+		fl6.flowi6_oif = READ_ONCE(sk->sk_bound_dev_if);
 
 	if (msg->msg_controllen) {
 		opt = &opt_space;
-- 
2.36.0.512.ge40c2bad7a-goog