tcp: annotate data-races around tp->notsent_lowat

tp->notsent_lowat can be read locklessly from do_tcp_getsockopt() and tcp_poll(). Fixes: c9bee3b ("tcp: TCP_NOTSENT_LOWAT socket option") Signed-off-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/20230719212857.3943972-10-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
mariux64 · Jul 20, 2023 · 1aeb87b · 1aeb87b
1 parent ae488c7
commit 1aeb87b
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Showing 2 changed files with 7 additions and 3 deletions.
diff --git a/include/net/tcp.h b/include/net/tcp.h
@@ -2061,7 +2061,11 @@ void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
 {
 	struct net *net = sock_net((struct sock *)tp);
-	return tp->notsent_lowat ?: READ_ONCE(net->ipv4.sysctl_tcp_notsent_lowat);
+	u32 val;
+
+	val = READ_ONCE(tp->notsent_lowat);
+
+	return val ?: READ_ONCE(net->ipv4.sysctl_tcp_notsent_lowat);
 }
 
 bool tcp_stream_memory_free(const struct sock *sk, int wake);

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
@@ -3664,7 +3664,7 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
 		err = tcp_repair_set_window(tp, optval, optlen);
 		break;
 	case TCP_NOTSENT_LOWAT:
-		tp->notsent_lowat = val;
+		WRITE_ONCE(tp->notsent_lowat, val);
 		sk->sk_write_space(sk);
 		break;
 	case TCP_INQ:
@@ -4164,7 +4164,7 @@ int do_tcp_getsockopt(struct sock *sk, int level,
 		val = tcp_time_stamp_raw() + READ_ONCE(tp->tsoffset);
 		break;
 	case TCP_NOTSENT_LOWAT:
-		val = tp->notsent_lowat;
+		val = READ_ONCE(tp->notsent_lowat);
 		break;
 	case TCP_INQ:
 		val = tp->recvmsg_inq;