[PATCH 5.15 061/201] tcp: sk->sk_bound_dev_if once in inet_request_bound_dev_if()

Greg Kroah-Hartman
2022-07-27T17:06:38Z

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 33344d54ad65..e71827aa2dfb 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