Re: [PATCH] tcp: possible race between tcp_done() and tcp_poll()
From: Eric Dumazet <hidden>
Date: 2017-03-30 03:18:06
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
On Thu, 2017-03-30 at 11:55 +0900, Seiichi Ikarashi wrote:
I got a report that receiving a RST packet but poll() got only POLLERR, no POLLIN|POLLRDHUP .
It was an old x86_64 kernel which does not include sk_state_{load,store} functions.
I suspected some race might have occur above.It looks that a one-liner patch would be enough in tcp_done() No need adding extra barriers Untested patch :
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 1e319a525d51b0b603a5ccc5143381c752b9f2c7..4107d3fc00a53f768cdb885971a1067c810f5c9f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c@@ -3285,12 +3285,12 @@ void tcp_done(struct sock *sk) if (sk->sk_state == TCP_SYN_SENT || sk->sk_state == TCP_SYN_RECV) TCP_INC_STATS(sock_net(sk), TCP_MIB_ATTEMPTFAILS); + sk->sk_shutdown = SHUTDOWN_MASK; tcp_set_state(sk, TCP_CLOSE); tcp_clear_xmit_timers(sk); if (req) reqsk_fastopen_remove(sk, req, false); - sk->sk_shutdown = SHUTDOWN_MASK; if (!sock_flag(sk, SOCK_DEAD)) sk->sk_state_change(sk);