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

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: 1ad98e9d1bdf ("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>

4 files changed, 10 insertions, 8 deletions

diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index a8cd5cf9ff5b..a80fd0ac4563 100644
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -130,11 +130,6 @@ static inline int inet_request_bound_dev_if(const struct sock *sk,
         return sk->sk_bound_dev_if;
 }
 
-static inline struct ip_options_rcu *ireq_opt_deref(const struct inet_request_sock *ireq)
-{
-        return rcu_dereference(ireq->ireq_opt);
-}
-
 struct inet_cork {
         unsigned int            flags;
         __be32                  addr;
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index b08feb219b44..8e08cea6f178 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -493,9 +493,11 @@ static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req
 
                 dh->dccph_checksum = dccp_v4_csum_finish(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);
         }
 
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index dfd5009f96ef..15e7f7915a21 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -544,7 +544,8 @@ struct dst_entry *inet_csk_route_req(const struct sock *sk,
         struct ip_options_rcu *opt;
         struct rtable *rt;
 
-        opt = ireq_opt_deref(ireq);
+        rcu_read_lock();
+        opt = rcu_dereference(ireq->ireq_opt);
 
         flowi4_init_output(fl4, ireq->ir_iif, ireq->ir_mark,
                            RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE,
@@ -558,11 +559,13 @@ struct dst_entry *inet_csk_route_req(const struct sock *sk,
                 goto no_route;
         if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway)
                 goto route_err;
+        rcu_read_unlock();
         return &rt->dst;
 
 route_err:
         ip_rt_put(rt);
 no_route:
+        rcu_read_unlock();
         __IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
         return NULL;
 }
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 44c09eddbb78..cd426313a298 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -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);
         }