tg import create t/mptcp-fix-inconsistent-state-on-fastopen-race

.topmsg

@@ -1,4 +1,89 @@
-From: Matthieu Baerts <matttbe@kernel.org>
-Subject: [PATCH] t/mptcp-fix-inconsistent-state-on-fastopen-race
+From: Paolo Abeni <pabeni@redhat.com>
+Subject: [PATCH] mptcp: fix inconsistent state on fastopen race
 
-Signed-off-by: Matthieu Baerts <matttbe@kernel.org>
+The netlink PM can race with fastopen self-connect attempts, shutting
+down the first subflow via:
+
+MPTCP_PM_CMD_DEL_ADDR -> mptcp_nl_remove_id_zero_address ->
+  mptcp_pm_nl_rm_subflow_received -> mptcp_close_ssk
+
+and transitioning such subflow to FIN_WAIT1 status before the syn-ack
+packet is processed. The MPTCP code does not react to such state change,
+leaving the connection in not-fallback status and the subflow handshake
+uncompleted, triggering the following splat:
+
+  WARNING: CPU: 0 PID: 10630 at net/mptcp/subflow.c:1405 subflow_data_ready+0x39f/0x690 net/mptcp/subflow.c:1405
+  Modules linked in:
+  CPU: 0 PID: 10630 Comm: kworker/u4:11 Not tainted 6.6.0-syzkaller-14500-g1c41041124bd #0
+  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
+  Workqueue: bat_events batadv_nc_worker
+  RIP: 0010:subflow_data_ready+0x39f/0x690 net/mptcp/subflow.c:1405
+  Code: 18 89 ee e8 e3 d2 21 f7 40 84 ed 75 1f e8 a9 d7 21 f7 44 89 fe bf 07 00 00 00 e8 0c d3 21 f7 41 83 ff 07 74 07 e8 91 d7 21 f7 <0f> 0b e8 8a d7 21 f7 48 89 df e8 d2 b2 ff ff 31 ff 89 c5 89 c6 e8
+  RSP: 0018:ffffc90000007448 EFLAGS: 00010246
+  RAX: 0000000000000000 RBX: ffff888031efc700 RCX: ffffffff8a65baf4
+  RDX: ffff888043222140 RSI: ffffffff8a65baff RDI: 0000000000000005
+  RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000007
+  R10: 000000000000000b R11: 0000000000000000 R12: 1ffff92000000e89
+  R13: ffff88807a534d80 R14: ffff888021c11a00 R15: 000000000000000b
+  FS:  0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
+  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
+  CR2: 00007fa19a0ffc81 CR3: 000000007a2db000 CR4: 00000000003506f0
+  DR0: 000000000000d8dd DR1: 0000000000000000 DR2: 0000000000000000
+  DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
+  Call Trace:
+   <IRQ>
+   tcp_data_ready+0x14c/0x5b0 net/ipv4/tcp_input.c:5128
+   tcp_data_queue+0x19c3/0x5190 net/ipv4/tcp_input.c:5208
+   tcp_rcv_state_process+0x11ef/0x4e10 net/ipv4/tcp_input.c:6844
+   tcp_v4_do_rcv+0x369/0xa10 net/ipv4/tcp_ipv4.c:1929
+   tcp_v4_rcv+0x3888/0x3b30 net/ipv4/tcp_ipv4.c:2329
+   ip_protocol_deliver_rcu+0x9f/0x480 net/ipv4/ip_input.c:205
+   ip_local_deliver_finish+0x2e4/0x510 net/ipv4/ip_input.c:233
+   NF_HOOK include/linux/netfilter.h:314 [inline]
+   NF_HOOK include/linux/netfilter.h:308 [inline]
+   ip_local_deliver+0x1b6/0x550 net/ipv4/ip_input.c:254
+   dst_input include/net/dst.h:461 [inline]
+   ip_rcv_finish+0x1c4/0x2e0 net/ipv4/ip_input.c:449
+   NF_HOOK include/linux/netfilter.h:314 [inline]
+   NF_HOOK include/linux/netfilter.h:308 [inline]
+   ip_rcv+0xce/0x440 net/ipv4/ip_input.c:569
+   __netif_receive_skb_one_core+0x115/0x180 net/core/dev.c:5527
+   __netif_receive_skb+0x1f/0x1b0 net/core/dev.c:5641
+   process_backlog+0x101/0x6b0 net/core/dev.c:5969
+   __napi_poll.constprop.0+0xb4/0x540 net/core/dev.c:6531
+   napi_poll net/core/dev.c:6600 [inline]
+   net_rx_action+0x956/0xe90 net/core/dev.c:6733
+   __do_softirq+0x21a/0x968 kernel/softirq.c:553
+   do_softirq kernel/softirq.c:454 [inline]
+   do_softirq+0xaa/0xe0 kernel/softirq.c:441
+   </IRQ>
+   <TASK>
+   __local_bh_enable_ip+0xf8/0x120 kernel/softirq.c:381
+   spin_unlock_bh include/linux/spinlock.h:396 [inline]
+   batadv_nc_purge_paths+0x1ce/0x3c0 net/batman-adv/network-coding.c:471
+   batadv_nc_worker+0x9b1/0x10e0 net/batman-adv/network-coding.c:722
+   process_one_work+0x884/0x15c0 kernel/workqueue.c:2630
+   process_scheduled_works kernel/workqueue.c:2703 [inline]
+   worker_thread+0x8b9/0x1290 kernel/workqueue.c:2784
+   kthread+0x33c/0x440 kernel/kthread.c:388
+   ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
+   ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
+   </TASK>
+
+To address the issue, catch the racing subflow state change and
+use it to cause the MPTCP fallback. Such fallback is also used to
+cause the first subflow state propagation to the msk socket via
+mptcp_set_connected(). After this change, the first subflow can
+additionally propagate the TCP_FIN_WAIT1 state, so rename the
+helper accordingly.
+
+Finally, if the state propagation is delayed to the msk release
+callback, the first subflow can change to a different state in between.
+Cache the relevant target state in a new msk-level field and use
+such value to update the msk state at release time.
+
+Fixes: 1e777f39b4d7 ("mptcp: add MSG_FASTOPEN sendmsg flag support")
+Reported-by: <syzbot+c53d4d3ddb327e80bc51@syzkaller.appspotmail.com>
+Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/458
+Signed-off-by: Paolo Abeni <pabeni@redhat.com>
+Reviewed-by: Mat Martineau <martineau@kernel.org>