[PATCH net-next] tcp: fix a lockdep issue in tcp_fastopen_reset_cipher()

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

icsk_accept_queue.fastopenq.lock is only fully initialized at listen()
time.

LOCKDEP is not happy if we attempt a spin_lock_bh() on it, because
of missing annotation. (Although kernel runs just fine)

Lets use net->ipv4.tcp_fastopen_ctx_lock to protect ctx access.

Fixes: 1fba70e5b6be ("tcp: socket option to set TCP fast open key")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Yuchung Cheng <ych...@google.com>
Cc: Christoph Paasch <cpaa...@apple.com>
---
 net/ipv4/tcp_fastopen.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 
e0a4b56644aa0f8ccd384644fde7e4841da29d3f..91762be58accaed7d8974e723b580fb3d7922fca
 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -92,20 +92,18 @@ error:              kfree(ctx);
        memcpy(ctx->key, key, len);
 
 
+       spin_lock(&net->ipv4.tcp_fastopen_ctx_lock);
        if (sk) {
                q = &inet_csk(sk)->icsk_accept_queue.fastopenq;
-               spin_lock_bh(&q->lock);
                octx = rcu_dereference_protected(q->ctx,
-                                                lockdep_is_held(&q->lock));
+                       lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
                rcu_assign_pointer(q->ctx, ctx);
-               spin_unlock_bh(&q->lock);
        } else {
-               spin_lock(&net->ipv4.tcp_fastopen_ctx_lock);
                octx = rcu_dereference_protected(net->ipv4.tcp_fastopen_ctx,
                        lockdep_is_held(&net->ipv4.tcp_fastopen_ctx_lock));
                rcu_assign_pointer(net->ipv4.tcp_fastopen_ctx, ctx);
-               spin_unlock(&net->ipv4.tcp_fastopen_ctx_lock);
        }
+       spin_unlock(&net->ipv4.tcp_fastopen_ctx_lock);
 
        if (octx)
                call_rcu(&octx->rcu, tcp_fastopen_ctx_free);