tcp: annotate data-races around fastopenq.max_qlen

This field can be read locklessly.

Fixes: 1536e2857bd3 ("tcp: Add a TCP_FASTOPEN socket option to get a max backlog on its listner")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20230719212857.3943972-12-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index b4c08ac..91a37c9 100644 (file)
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -513,7 +513,7 @@ static inline void fastopen_queue_tune(struct sock *sk, int backlog)
        struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
        int somaxconn = READ_ONCE(sock_net(sk)->core.sysctl_somaxconn);
 
-       queue->fastopenq.max_qlen = min_t(unsigned int, backlog, somaxconn);
+       WRITE_ONCE(queue->fastopenq.max_qlen, min_t(unsigned int, backlog, somaxconn));
 }
 
 static inline void tcp_move_syn(struct tcp_sock *tp,

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 3e137e9..8ed52e1 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4145,7 +4145,7 @@ int do_tcp_getsockopt(struct sock *sk, int level,
                break;
 
        case TCP_FASTOPEN:
-               val = icsk->icsk_accept_queue.fastopenq.max_qlen;
+               val = READ_ONCE(icsk->icsk_accept_queue.fastopenq.max_qlen);
                break;
 
        case TCP_FASTOPEN_CONNECT:

diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 45cc7f1..85e4953 100644 (file)
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -296,6 +296,7 @@ static struct sock *tcp_fastopen_create_child(struct sock *sk,
 static bool tcp_fastopen_queue_check(struct sock *sk)
 {
        struct fastopen_queue *fastopenq;
+       int max_qlen;
 
        /* Make sure the listener has enabled fastopen, and we don't
         * exceed the max # of pending TFO requests allowed before trying
@@ -308,10 +309,11 @@ static bool tcp_fastopen_queue_check(struct sock *sk)
         * temporarily vs a server not supporting Fast Open at all.
         */
        fastopenq = &inet_csk(sk)->icsk_accept_queue.fastopenq;
-       if (fastopenq->max_qlen == 0)
+       max_qlen = READ_ONCE(fastopenq->max_qlen);
+       if (max_qlen == 0)
                return false;
 
-       if (fastopenq->qlen >= fastopenq->max_qlen) {
+       if (fastopenq->qlen >= max_qlen) {
                struct request_sock *req1;
                spin_lock(&fastopenq->lock);
                req1 = fastopenq->rskq_rst_head;