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tcp/dccp: fix lockdep splat in inet_csk_route_req()

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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: c92e8c02fe ("tcp/dccp: fix ireq->opt races")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2017-10-22 12:33:57 -07:00 committed by David S. Miller
parent 3a91d29f20
commit a6ca7abe53
1 changed files with 2 additions and 1 deletions
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3
net/ipv4/inet_connection_sock.c
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@ -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),