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inet: make sure to grab rcu_read_lock before using ireq->ireq_opt

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Timer handlers do not imply rcu_read_lock(), so my recent fix
triggered a LOCKDEP warning when SYNACK is retransmit.

Lets add rcu_read_lock()/rcu_read_unlock() pairs around ireq->ireq_opt
usages instead of guessing what is done by callers, since it is
not worth the pain.

Get rid of ireq_opt_deref() helper since it hides the logic
without real benefit, since it is now a standard rcu_dereference().

Fixes: 1ad98e9d1b ("tcp/dccp: fix lockdep issue when SYN is backlogged")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2018-10-02 12:35:05 -07:00 • committed by David S. Miller
parent ff58e2df62
commit 2ab2ddd301
4 changed files with 10 additions and 8 deletions
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4
net/ipv4/tcp_ipv4.c
View file

@ -943,9 +943,11 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
if (skb) {
__tcp_v4_send_check(skb, ireq->ir_loc_addr, ireq->ir_rmt_addr);
rcu_read_lock();
err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,
ireq->ir_rmt_addr,
ireq_opt_deref(ireq));
rcu_dereference(ireq->ireq_opt));
rcu_read_unlock();
err = net_xmit_eval(err);
}