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authorEric Dumazet <edumazet@google.com>2017-10-24 08:20:31 -0700
committerDavid S. Miller <davem@davemloft.net>2017-10-26 17:41:32 +0900
commit06f877d613be3621604c2520ec0351d9fbdca15f (patch)
treec7408afed6ebde2a04f1ee9bdd7932780f7e64fe /net/dccp
parentrds: Fix inaccurate accounting of unsignaled wrs (diff)
downloadlinux-dev-06f877d613be3621604c2520ec0351d9fbdca15f.tar.xz
linux-dev-06f877d613be3621604c2520ec0351d9fbdca15f.zip
tcp/dccp: fix other lockdep splats accessing ireq_opt
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 <edumazet@google.com> Reported-by: kernel test robot <fengguang.wu@intel.com> Reported-by: Maciej ┼╗enczykowski <maze@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/dccp')
-rw-r--r--net/dccp/ipv4.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 0490916864f9..e65fcb45c3f6 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -495,7 +495,7 @@ static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req
ireq->ir_rmt_addr);
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);
}