This is a note to let you know that I've just added the patch titled

tcp/dccp: fix lockdep splat in inet_csk_route_req()

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: tcp-dccp-fix-lockdep-splat-in-inet_csk_route_req.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Nov 16 15:08:14 CET 2017

From: Eric Dumazet edumazet@google.com Date: Sun, 22 Oct 2017 12:33:57 -0700 Subject: tcp/dccp: fix lockdep splat in inet_csk_route_req()

From: Eric Dumazet edumazet@google.com

[ Upstream commit a6ca7abe53633d08eea1c6756cb49c9b2d4c90bf ]

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: c92e8c02fe66 ("tcp/dccp: fix ireq->opt races") Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/inet_connection_sock.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -415,7 +415,8 @@ struct dst_entry *inet_csk_route_req(con struct ip_options_rcu *opt; struct rtable *rt;

- opt = rcu_dereference(ireq->ireq_opt); + opt = rcu_dereference_protected(ireq->ireq_opt, + atomic_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),

Patches currently in stable-queue which might be from edumazet@google.com are

queue-4.4/tcp-dccp-fix-ireq-opt-races.patch queue-4.4/tcp-fix-tcp_mtu_probe-vs-highest_sack.patch queue-4.4/ipv6-flowlabel-do-not-leave-opt-tot_len-with-garbage.patch queue-4.4/packet-avoid-panic-in-packet_getsockopt.patch queue-4.4/sctp-add-the-missing-sock_owned_by_user-check-in-sctp_icmp_redirect.patch queue-4.4/tun-tap-sanitize-tunsetsndbuf-input.patch queue-4.4/tcp-dccp-fix-lockdep-splat-in-inet_csk_route_req.patch queue-4.4/tcp-dccp-fix-other-lockdep-splats-accessing-ireq_opt.patch