From 06f877d613be3621604c2520ec0351d9fbdca15f Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 24 Oct 2017 08:20:31 -0700 Subject: tcp/dccp: fix other lockdep splats accessing ireq_opt MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In my first attempt to fix the lockdep splat, I forgot we could enter inet_csk_route_req() with a freshly allocated request socket, for which refcount has not yet been elevated, due to complex SLAB_TYPESAFE_BY_RCU rules. We either are in rcu_read_lock() section _or_ we own a refcount on the request. Correct RCU verb to use here is rcu_dereference_check(), although it is not possible to prove we actually own a reference on a shared refcount :/ In v2, I added ireq_opt_deref() helper and use in three places, to fix other possible splats. [ 49.844590] lockdep_rcu_suspicious+0xea/0xf3 [ 49.846487] inet_csk_route_req+0x53/0x14d [ 49.848334] tcp_v4_route_req+0xe/0x10 [ 49.850174] tcp_conn_request+0x31c/0x6a0 [ 49.851992] ? __lock_acquire+0x614/0x822 [ 49.854015] tcp_v4_conn_request+0x5a/0x79 [ 49.855957] ? tcp_v4_conn_request+0x5a/0x79 [ 49.858052] tcp_rcv_state_process+0x98/0xdcc [ 49.859990] ? sk_filter_trim_cap+0x2f6/0x307 [ 49.862085] tcp_v4_do_rcv+0xfc/0x145 [ 49.864055] ? tcp_v4_do_rcv+0xfc/0x145 [ 49.866173] tcp_v4_rcv+0x5ab/0xaf9 [ 49.868029] ip_local_deliver_finish+0x1af/0x2e7 [ 49.870064] ip_local_deliver+0x1b2/0x1c5 [ 49.871775] ? inet_del_offload+0x45/0x45 [ 49.873916] ip_rcv_finish+0x3f7/0x471 [ 49.875476] ip_rcv+0x3f1/0x42f [ 49.876991] ? ip_local_deliver_finish+0x2e7/0x2e7 [ 49.878791] __netif_receive_skb_core+0x6d3/0x950 [ 49.880701] ? process_backlog+0x7e/0x216 [ 49.882589] __netif_receive_skb+0x1d/0x5e [ 49.884122] process_backlog+0x10c/0x216 [ 49.885812] net_rx_action+0x147/0x3df Fixes: a6ca7abe53633 ("tcp/dccp: fix lockdep splat in inet_csk_route_req()") Fixes: c92e8c02fe66 ("tcp/dccp: fix ireq->opt races") Signed-off-by: Eric Dumazet Reported-by: kernel test robot Reported-by: Maciej Żenczykowski Signed-off-by: David S. Miller --- net/ipv4/inet_connection_sock.c | 4 ++-- net/ipv4/tcp_ipv4.c | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c index 18cd2eae758f..b47a59cb3573 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -543,8 +543,8 @@ struct dst_entry *inet_csk_route_req(const struct sock *sk, struct ip_options_rcu *opt; struct rtable *rt; - opt = rcu_dereference_protected(ireq->ireq_opt, - refcount_read(&req->rsk_refcnt) > 0); + opt = ireq_opt_deref(ireq); + 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), diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 4c43365c374c..5b027c69cbc5 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -877,7 +877,7 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst, err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr, ireq->ir_rmt_addr, - rcu_dereference(ireq->ireq_opt)); + ireq_opt_deref(ireq)); err = net_xmit_eval(err); } -- cgit v1.2.3-58-ga151