tcp: annotate data races around tp->mtu_info

While tp->mtu_info is read while socket is owned, the write
sides happen from err handlers (tcp_v[46]_mtu_reduced)
which only own the socket spinlock.

Fixes: 563d34d05786 ("tcp: dont drop MTU reduction indications")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index e66ad6b..b9dc2d6 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -342,7 +342,7 @@ void tcp_v4_mtu_reduced(struct sock *sk)
 
        if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE))
                return;
-       mtu = tcp_sk(sk)->mtu_info;
+       mtu = READ_ONCE(tcp_sk(sk)->mtu_info);
        dst = inet_csk_update_pmtu(sk, mtu);
        if (!dst)
                return;
@@ -546,7 +546,7 @@ int tcp_v4_err(struct sk_buff *skb, u32 info)
                        if (sk->sk_state == TCP_LISTEN)
                                goto out;
 
-                       tp->mtu_info = info;
+                       WRITE_ONCE(tp->mtu_info, info);
                        if (!sock_owned_by_user(sk)) {
                                tcp_v4_mtu_reduced(sk);
                        } else {

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 578ab63..593c32f 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -352,7 +352,7 @@ static void tcp_v6_mtu_reduced(struct sock *sk)
        if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE))
                return;
 
-       dst = inet6_csk_update_pmtu(sk, tcp_sk(sk)->mtu_info);
+       dst = inet6_csk_update_pmtu(sk, READ_ONCE(tcp_sk(sk)->mtu_info));
        if (!dst)
                return;
 
@@ -443,7 +443,7 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
                if (!ip6_sk_accept_pmtu(sk))
                        goto out;
 
-               tp->mtu_info = ntohl(info);
+               WRITE_ONCE(tp->mtu_info, ntohl(info));
                if (!sock_owned_by_user(sk))
                        tcp_v6_mtu_reduced(sk);
                else if (!test_and_set_bit(TCP_MTU_REDUCED_DEFERRED,