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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Eric Dumazet <edumazet@google.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10 258/545] tcp: sk->sk_bound_dev_if once in inet_request_bound_dev_if()
Date:   Fri, 19 Aug 2022 17:40:28 +0200
Message-Id: <20220819153840.900835053@linuxfoundation.org>
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From: Eric Dumazet <edumazet@google.com>

[ Upstream commit fdb5fd7f736ec7ae9fb36d2842ea6d9ebc4e7269 ]

inet_request_bound_dev_if() reads sk->sk_bound_dev_if twice
while listener socket is not locked.

Another cpu could change this field under us.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/net/inet_sock.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index 3c039d4b0e48..886ed0950b7f 100644
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -117,14 +117,15 @@ static inline u32 inet_request_mark(const struct sock *sk, struct sk_buff *skb)
 static inline int inet_request_bound_dev_if(const struct sock *sk,
 					    struct sk_buff *skb)
 {
+	int bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
 #ifdef CONFIG_NET_L3_MASTER_DEV
 	struct net *net = sock_net(sk);
 
-	if (!sk->sk_bound_dev_if && net->ipv4.sysctl_tcp_l3mdev_accept)
+	if (!bound_dev_if && net->ipv4.sysctl_tcp_l3mdev_accept)
 		return l3mdev_master_ifindex_by_index(net, skb->skb_iif);
 #endif
 
-	return sk->sk_bound_dev_if;
+	return bound_dev_if;
 }
 
 static inline int inet_sk_bound_l3mdev(const struct sock *sk)
-- 
2.35.1