udp: Fix a data-race around sysctl_udp_l3mdev_accept.

[ Upstream commit 3d72bb4188c708bb16758c60822fc4dda7a95174 ]

While reading sysctl_udp_l3mdev_accept, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.

Fixes: 63a6fff353d0 ("net: Avoid receiving packets with an l3mdev on unbound UDP sockets")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/include/net/udp.h b/include/net/udp.h
index 909ecf4..438b1b0 100644 (file)
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -262,7 +262,7 @@ static inline bool udp_sk_bound_dev_eq(struct net *net, int bound_dev_if,
                                       int dif, int sdif)
 {
 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
-       return inet_bound_dev_eq(!!net->ipv4.sysctl_udp_l3mdev_accept,
+       return inet_bound_dev_eq(!!READ_ONCE(net->ipv4.sysctl_udp_l3mdev_accept),
                                 bound_dev_if, dif, sdif);
 #else
        return inet_bound_dev_eq(true, bound_dev_if, dif, sdif);