Re: [PATCH] tcp: possible race between tcp_done() and tcp_poll()
From: Seiichi Ikarashi <hidden>
Date: 2017-03-30 03:49:48
On 2017-03-30 12:18, Eric Dumazet wrote:
On Thu, 2017-03-30 at 11:55 +0900, Seiichi Ikarashi wrote:quoted
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
I agree. sk->sk_shutdown seems not affect the behavior of both tcp_clear_xmit_timers() and reqsk_fastopen_remove().
Untested patch :
Sorry, I cannot test it because I do not have a replication environment.
quoted hunk ↗ jump to hunk
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);