tcp: annotate data-races around tp->rx_opt.user_mss

This field is already read locklessly for listeners,
next patch will make setsockopt(TCP_MAXSEG) lockless.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Link: https://patch.msgid.link/20250821141901.18839-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c
index 2e7c2691a1933e5c8d9dc71ec99a5d92970ad7cd..000116e47e38d90802c5dd676c0659fab19bcff3 100644 (file)
--- a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c
+++ b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c
@@ -951,6 +951,7 @@ static unsigned int chtls_select_mss(const struct chtls_sock *csk,
        struct tcp_sock *tp;
        unsigned int mss;
        struct sock *sk;
+       u16 user_mss;
 
        mss = ntohs(req->tcpopt.mss);
        sk = csk->sk;
@@ -969,8 +970,9 @@ static unsigned int chtls_select_mss(const struct chtls_sock *csk,
                tcpoptsz += round_up(TCPOLEN_TIMESTAMP, 4);
 
        tp->advmss = dst_metric_advmss(dst);
-       if (USER_MSS(tp) && tp->advmss > USER_MSS(tp))
-               tp->advmss = USER_MSS(tp);
+       user_mss = USER_MSS(tp);
+       if (user_mss && tp->advmss > user_mss)
+               tp->advmss = user_mss;
        if (tp->advmss > pmtu - iphdrsz)
                tp->advmss = pmtu - iphdrsz;
        if (mss && tp->advmss > mss)

diff --git a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h
index 2285cf2df251db9ec84d305d5ffa012279f6c43f..667effc2a23cb78901d65da2712a7e8a66ec81b4 100644 (file)
--- a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h
+++ b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h
@@ -90,7 +90,7 @@ struct deferred_skb_cb {
 
 #define SND_WSCALE(tp) ((tp)->rx_opt.snd_wscale)
 #define RCV_WSCALE(tp) ((tp)->rx_opt.rcv_wscale)
-#define USER_MSS(tp) ((tp)->rx_opt.user_mss)
+#define USER_MSS(tp) (READ_ONCE((tp)->rx_opt.user_mss))
 #define TS_RECENT_STAMP(tp) ((tp)->rx_opt.ts_recent_stamp)
 #define WSCALE_OK(tp) ((tp)->rx_opt.wscale_ok)
 #define TSTAMP_OK(tp) ((tp)->rx_opt.tstamp_ok)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 71a956fbfc5533224ee00e792de2cfdccd4d40aa..a12d81e01b3f2fb964227881c2f779741cc06e58 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3760,7 +3760,7 @@ int tcp_sock_set_maxseg(struct sock *sk, int val)
        if (val && (val < TCP_MIN_MSS || val > MAX_TCP_WINDOW))
                return -EINVAL;
 
-       tcp_sk(sk)->rx_opt.user_mss = val;
+       WRITE_ONCE(tcp_sk(sk)->rx_opt.user_mss, val);
        return 0;
 }
 
@@ -4383,6 +4383,7 @@ int do_tcp_getsockopt(struct sock *sk, int level,
        struct inet_connection_sock *icsk = inet_csk(sk);
        struct tcp_sock *tp = tcp_sk(sk);
        struct net *net = sock_net(sk);
+       int user_mss;
        int val, len;
 
        if (copy_from_sockptr(&len, optlen, sizeof(int)))
@@ -4396,9 +4397,10 @@ int do_tcp_getsockopt(struct sock *sk, int level,
        switch (optname) {
        case TCP_MAXSEG:
                val = tp->mss_cache;
-               if (tp->rx_opt.user_mss &&
+               user_mss = READ_ONCE(tp->rx_opt.user_mss);
+               if (user_mss &&
                    ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)))
-                       val = tp->rx_opt.user_mss;
+                       val = user_mss;
                if (tp->repair)
                        val = tp->rx_opt.mss_clamp;
                break;

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 71b76e98371a667b6e8263b32c242363672d7c5a..7b537978dfe6b436c723815f1ce64f05f9c1ae61 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6297,7 +6297,7 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
        u16 mss = tp->rx_opt.mss_clamp, try_exp = 0;
        bool syn_drop = false;
 
-       if (mss == tp->rx_opt.user_mss) {
+       if (mss == READ_ONCE(tp->rx_opt.user_mss)) {
                struct tcp_options_received opt;
 
                /* Get original SYNACK MSS value if user MSS sets mss_clamp */
@@ -7117,7 +7117,7 @@ u16 tcp_get_syncookie_mss(struct request_sock_ops *rsk_ops,
                return 0;
        }
 
-       mss = tcp_parse_mss_option(th, tp->rx_opt.user_mss);
+       mss = tcp_parse_mss_option(th, READ_ONCE(tp->rx_opt.user_mss));
        if (!mss)
                mss = af_ops->mss_clamp;
 
@@ -7131,7 +7131,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 {
        struct tcp_fastopen_cookie foc = { .len = -1 };
        struct tcp_options_received tmp_opt;
-       struct tcp_sock *tp = tcp_sk(sk);
+       const struct tcp_sock *tp = tcp_sk(sk);
        struct net *net = sock_net(sk);
        struct sock *fastopen_sk = NULL;
        struct request_sock *req;
@@ -7182,7 +7182,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 
        tcp_clear_options(&tmp_opt);
        tmp_opt.mss_clamp = af_ops->mss_clamp;
-       tmp_opt.user_mss  = tp->rx_opt.user_mss;
+       tmp_opt.user_mss  = READ_ONCE(tp->rx_opt.user_mss);
        tcp_parse_options(sock_net(sk), skb, &tmp_opt, 0,
                          want_cookie ? NULL : &foc);
 

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index dfbac0876d96ee6b556fff5b6c9ec8fe2e04aa05..86892c8672ed49a49b85530b648d695ed171a3c8 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3890,6 +3890,7 @@ static void tcp_connect_init(struct sock *sk)
        const struct dst_entry *dst = __sk_dst_get(sk);
        struct tcp_sock *tp = tcp_sk(sk);
        __u8 rcv_wscale;
+       u16 user_mss;
        u32 rcv_wnd;
 
        /* We'll fix this up when we get a response from the other end.
@@ -3902,8 +3903,9 @@ static void tcp_connect_init(struct sock *sk)
        tcp_ao_connect_init(sk);
 
        /* If user gave his TCP_MAXSEG, record it to clamp */
-       if (tp->rx_opt.user_mss)
-               tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
+       user_mss = READ_ONCE(tp->rx_opt.user_mss);
+       if (user_mss)
+               tp->rx_opt.mss_clamp = user_mss;
        tp->max_window = 0;
        tcp_mtup_init(sk);
        tcp_sync_mss(sk, dst_mtu(dst));