tcp/dccp: Fix a data-race around sysctl_tcp_fwmark_accept.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2149949


Upstream Status: linux.git

commit 1a0008f9
Author: Kuniyuki Iwashima <kuniyu@amazon.com>
Date:   Wed Jul 13 13:51:58 2022 -0700

    tcp/dccp: Fix a data-race around sysctl_tcp_fwmark_accept.

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

    Fixes: 84f39b08 ("net: support marking accepting TCP sockets")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Guillaume Nault <gnault@redhat.com>

include/net/inet_sock.h

@@ -107,7 +107,8 @@ static inline struct inet_request_sock *inet_rsk(const struct request_sock *sk)
 
 static inline u32 inet_request_mark(const struct sock *sk, struct sk_buff *skb)
 {
-	if (!sk->sk_mark && sock_net(sk)->ipv4.sysctl_tcp_fwmark_accept)
+	if (!sk->sk_mark &&
+	    READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fwmark_accept))
 		return skb->mark;
 
 	return sk->sk_mark;