From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH net] tcp/dccp: fix lockdep splat in inet_csk_route_req() Date: Sun, 22 Oct 2017 12:33:57 -0700 Message-ID: <1508700837.30291.63.camel@edumazet-glaptop3.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev To: David Miller Return-path: Received: from mail-pg0-f67.google.com ([74.125.83.67]:53404 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932128AbdJVTeA (ORCPT ); Sun, 22 Oct 2017 15:34:00 -0400 Received: by mail-pg0-f67.google.com with SMTP id s2so10163219pge.10 for ; Sun, 22 Oct 2017 12:34:00 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet This patch fixes the following lockdep splat in inet_csk_route_req() lockdep_rcu_suspicious inet_csk_route_req tcp_v4_send_synack tcp_rtx_synack inet_rtx_syn_ack tcp_fastopen_synack_time tcp_retransmit_timer tcp_write_timer_handler tcp_write_timer call_timer_fn Thread running inet_csk_route_req() owns a reference on the request socket, so we have the guarantee ireq->ireq_opt wont be changed or freed. lockdep can enforce this invariant for us. Fixes: c92e8c02fe66 ("tcp/dccp: fix ireq->opt races") Signed-off-by: Eric Dumazet --- net/ipv4/inet_connection_sock.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c index 5ec9136a7c36933cb36e5cd50058eb6cf189a7c3..18cd2eae758ff1a9d8a736e143417c7007b99067 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -543,7 +543,8 @@ struct dst_entry *inet_csk_route_req(const struct sock *sk, struct ip_options_rcu *opt; struct rtable *rt; - opt = rcu_dereference(ireq->ireq_opt); + opt = rcu_dereference_protected(ireq->ireq_opt, + refcount_read(&req->rsk_refcnt) > 0); flowi4_init_output(fl4, ireq->ir_iif, ireq->ir_mark, RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE, sk->sk_protocol, inet_sk_flowi_flags(sk),