4.9-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 2ab2ddd301a22ca3c5f0b743593e4ad2953dfa53 ]
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/net/inet_sock.h | 5 ----- net/dccp/ipv4.c | 4 +++- net/ipv4/inet_connection_sock.c | 5 ++++- net/ipv4/tcp_ipv4.c | 4 +++- 4 files changed, 10 insertions(+), 8 deletions(-)
--- a/include/net/inet_sock.h +++ b/include/net/inet_sock.h @@ -132,11 +132,6 @@ static inline int inet_request_bound_dev 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; --- a/net/dccp/ipv4.c +++ b/net/dccp/ipv4.c @@ -493,9 +493,11 @@ static int dccp_v4_send_response(const s
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); }
--- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -410,7 +410,8 @@ struct dst_entry *inet_csk_route_req(con 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, @@ -424,11 +425,13 @@ struct dst_entry *inet_csk_route_req(con 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; } --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -859,9 +859,11 @@ static int tcp_v4_send_synack(const stru 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); }