======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.3.4258/16436 is trying to acquire lock:
ffffffff8ea848a0 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_node_track_caller_noprof+0xbc/0x730

but task is already holding lock:
ffff8881170160e0 (k-sk_lock-AF_INET6/1){+.+.}-{0:0}, at: mptcp_check_listen_stop+0x1a6/0x2b0

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #8 (k-sk_lock-AF_INET6/1){+.+.}-{0:0}:
       lock_sock_nested+0x41/0x100
       mptcp_subflow_create_socket+0x144/0x810
       __mptcp_nmpc_sk+0x155/0x770
       mptcp_connect+0x6f/0x7a0
       __inet_stream_connect+0x258/0xe00
       inet_stream_connect+0x66/0xa0
       __sys_connect+0x323/0x460
       __x64_sys_connect+0x7a/0x90
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #7 (sk_lock-AF_INET6){+.+.}-{0:0}:
       lock_sock_nested+0x41/0x100
       tls_sw_sendmsg+0x161/0x2860
       sock_sendmsg_nosec+0x90/0x180
       __sys_sendto+0x408/0x5a0
       __x64_sys_sendto+0xde/0x100
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (&ctx->tx_lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       tls_sw_sendmsg+0x13c/0x2860
       sock_sendmsg_nosec+0x90/0x180
       sock_sendmsg+0x1ca/0x2d0
       __sock_xmit+0x245/0x4f0
       nbd_disconnect+0x3ad/0x560
       nbd_disconnect_and_put+0x32/0x280
       nbd_genl_disconnect+0x4af/0x590
       genl_family_rcv_msg_doit+0x233/0x340
       genl_rcv_msg+0x614/0x7a0
       netlink_rcv_skb+0x226/0x4a0
       genl_rcv+0x28/0x40
       netlink_unicast+0x7bb/0x940
       netlink_sendmsg+0x813/0xb40
       sock_sendmsg_nosec+0x13a/0x180
       ____sys_sendmsg+0x54e/0x850
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1b1/0x290
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       nbd_queue_rq+0x373/0x1150
       blk_mq_dispatch_rq_list+0x499/0x1990
       __blk_mq_sched_dispatch_requests+0xd36/0x1580
       blk_mq_sched_dispatch_requests+0xd7/0x190
       blk_mq_run_work_fn+0x16c/0x300
       process_scheduled_works+0xa8e/0x14e0
       worker_thread+0xa47/0xfb0
       kthread+0x388/0x470
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #4 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       nbd_queue_rq+0xc1/0x1150
       blk_mq_dispatch_rq_list+0x499/0x1990
       __blk_mq_sched_dispatch_requests+0xd36/0x1580
       blk_mq_sched_dispatch_requests+0xd7/0x190
       blk_mq_run_work_fn+0x16c/0x300
       process_scheduled_works+0xa8e/0x14e0
       worker_thread+0xa47/0xfb0
       kthread+0x388/0x470
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #3 (set->srcu){.+.+}-{0:0}:
       __synchronize_srcu+0xc9/0x2f0
       elevator_switch+0x1e8/0x7b0
       elevator_change+0x2fa/0x480
       elevator_set_default+0x375/0x440
       blk_register_queue+0x3f3/0x4e0
       __add_disk+0x6cb/0xe30
       add_disk_fwnode+0xfb/0x4b0
       nbd_dev_add+0x733/0xb60
       nbd_init+0x15f/0x1e0
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x1d/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #2 (&q->elevator_lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       elevator_change+0x1af/0x480
       elevator_set_none+0xb5/0x140
       blk_mq_update_nr_hw_queues+0x5ef/0x19f0
       nbd_start_device+0x189/0xb30
       nbd_genl_connect+0x1597/0x1c10
       genl_family_rcv_msg_doit+0x233/0x340
       genl_rcv_msg+0x614/0x7a0
       netlink_rcv_skb+0x226/0x4a0
       genl_rcv+0x28/0x40
       netlink_unicast+0x7bb/0x940
       netlink_sendmsg+0x813/0xb40
       sock_sendmsg_nosec+0x13a/0x180
       ____sys_sendmsg+0x54e/0x850
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1b1/0x290
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&q->q_usage_counter(io)#52){++++}-{0:0}:
       blk_alloc_queue+0x544/0x690
       __blk_mq_alloc_disk+0x194/0x390
       nbd_dev_add+0x494/0xb60
       nbd_init+0x15f/0x1e0
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x1d/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #0 (fs_reclaim){+.+.}-{0:0}:
       __lock_acquire+0x1520/0x2cf0
       lock_acquire+0x106/0x350
       fs_reclaim_acquire+0x71/0x100
       __kmalloc_node_track_caller_noprof+0xbc/0x730
       __alloc_skb+0x2bd/0x7a0
       mptcp_event_pm_listener+0x135/0x560
       mptcp_check_listen_stop+0x1d3/0x2b0
       __mptcp_close+0xf5/0xda0
       mptcp_close+0x28/0x1a0
       inet_release+0x143/0x190
       sock_close+0xad/0x220
       __fput+0x418/0xa50
       task_work_run+0x1d9/0x270
       exit_to_user_mode_loop+0x1fa/0x730
       do_syscall_64+0x353/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  fs_reclaim --> sk_lock-AF_INET6 --> k-sk_lock-AF_INET6/1

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(k-sk_lock-AF_INET6/1);
                               lock(sk_lock-AF_INET6);
                               lock(k-sk_lock-AF_INET6/1);
  lock(fs_reclaim);

 *** DEADLOCK ***

3 locks held by syz.3.4258/16436:
 #0: ffff8881aa880e40 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: sock_close+0x82/0x220
 #1: ffff88801f37a960 (sk_lock-AF_INET6){+.+.}-{0:0}, at: mptcp_close+0x1d/0x1a0
 #2: ffff8881170160e0 (k-sk_lock-AF_INET6/1){+.+.}-{0:0}, at: mptcp_check_listen_stop+0x1a6/0x2b0

stack backtrace:
CPU: 0 UID: 0 PID: 16436 Comm: syz.3.4258 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 print_circular_bug+0x2e1/0x300
 check_noncircular+0x12e/0x150
 __lock_acquire+0x1520/0x2cf0
 lock_acquire+0x106/0x350
 fs_reclaim_acquire+0x71/0x100
 __kmalloc_node_track_caller_noprof+0xbc/0x730
 __alloc_skb+0x2bd/0x7a0
 mptcp_event_pm_listener+0x135/0x560
 mptcp_check_listen_stop+0x1d3/0x2b0
 __mptcp_close+0xf5/0xda0
 mptcp_close+0x28/0x1a0
 inet_release+0x143/0x190
 sock_close+0xad/0x220
 __fput+0x418/0xa50
 task_work_run+0x1d9/0x270
 exit_to_user_mode_loop+0x1fa/0x730
 do_syscall_64+0x353/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff5e299ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffec48993d8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffec48994c0 RCX: 00007ff5e299ce59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00000000000595d7 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2c520000 R11: 0000000000000246 R12: 00007ffec4899500
R13: 00007ff5e2c15fac R14: 0000000000059626 R15: 00007ff5e2c15fa0
 </TASK>
