======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.9265/13283 is trying to acquire lock:
ffffffff8ee90400 (fs_reclaim){+.+.}-{0:0}, at: prepare_alloc_pages+0x149/0x600

but task is already holding lock:
ffff888103e86858 (&hugetlb_fault_mutex_table[i]){+.+.}-{4:4}, at: hugetlb_fault+0x3b5/0x1440

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #7 (&hugetlb_fault_mutex_table[i]){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       hugetlb_fault+0x3b5/0x1440
       handle_mm_fault+0x24fc/0x3750
       do_user_addr_fault+0x746/0x1340
       exc_page_fault+0x6a/0xc0
       asm_exc_page_fault+0x26/0x30
       rep_movs_alternative+0x75/0xa0
       _copy_from_iter+0x21b/0x1660
       sk_msg_memcopy_from_iter+0x35e/0x700
       tls_sw_sendmsg+0x1c20/0x2c00
       sock_sendmsg_nosec+0x90/0x190
       __sys_sendto+0x408/0x5a0
       __x64_sys_sendto+0xde/0x100
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (sk_lock-AF_INET6){+.+.}-{0:0}:
       lock_sock_nested+0x41/0x100
       inet_shutdown+0x6a/0x390
       nbd_mark_nsock_dead+0x2cb/0x550
       recv_work+0x1cee/0x1e10
       process_scheduled_works+0xc3d/0x1630
       worker_thread+0xa47/0xfb0
       kthread+0x38b/0x480
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       nbd_queue_rq+0x373/0xff0
       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+0xc3d/0x1630
       worker_thread+0xa47/0xfb0
       kthread+0x38b/0x480
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #4 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       nbd_queue_rq+0xc1/0xff0
       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+0xc3d/0x1630
       worker_thread+0xa47/0xfb0
       kthread+0x38b/0x480
       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+0x6b8/0xdb0
       add_disk_fwnode+0x100/0x3a0
       nbd_dev_add+0x733/0xb60
       nbd_init+0x168/0x1f0
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x22/0x1d0
       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+0x167d/0x1cd0
       genl_family_rcv_msg_doit+0x233/0x340
       genl_rcv_msg+0x614/0x7a0
       netlink_rcv_skb+0x226/0x4a0
       genl_rcv+0x28/0x40
       netlink_unicast+0x7bd/0x940
       netlink_sendmsg+0x813/0xb40
       sock_sendmsg_nosec+0x14e/0x190
       ____sys_sendmsg+0x54e/0x850
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1b1/0x290
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&q->q_usage_counter(io)#51){++++}-{0:0}:
       blk_alloc_queue+0x544/0x690
       __blk_mq_alloc_disk+0x194/0x390
       nbd_dev_add+0x494/0xb60
       nbd_init+0x168/0x1f0
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x22/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #0 (fs_reclaim){+.+.}-{0:0}:
       __lock_acquire+0x164c/0x2de0
       lock_acquire+0x115/0x350
       fs_reclaim_acquire+0x71/0x100
       prepare_alloc_pages+0x149/0x600
       __alloc_frozen_pages_noprof+0x185/0x5a0
       alloc_pages_mpol+0x21e/0x390
       alloc_pages_noprof+0xb1/0x2b0
       __pud_alloc+0x3a/0x460
       huge_pte_alloc+0x4f6/0x630
       hugetlb_fault+0x412/0x1440
       handle_mm_fault+0x24fc/0x3750
       do_user_addr_fault+0xa4f/0x1340
       exc_page_fault+0x6a/0xc0
       asm_exc_page_fault+0x26/0x30

other info that might help us debug this:

Chain exists of:
  fs_reclaim --> sk_lock-AF_INET6 --> &hugetlb_fault_mutex_table[i]

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&hugetlb_fault_mutex_table[i]);
                               lock(sk_lock-AF_INET6);
                               lock(&hugetlb_fault_mutex_table[i]);
  lock(fs_reclaim);

 *** DEADLOCK ***

locks held by syz.2.9265/13283: 2, last CPU#1:
 #0: ffff888160788688 (vm_lock){++++}-{0:0}, at: lock_vma_under_rcu+0x1d1/0x500
 #1: ffff888103e86858 (&hugetlb_fault_mutex_table[i]){+.+.}-{4:4}, at: hugetlb_fault+0x3b5/0x1440

stack backtrace:
CPU: 1 UID: 0 PID: 13283 Comm: syz.2.9265 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+0x2e2/0x300
 check_noncircular+0x12f/0x150
 __lock_acquire+0x164c/0x2de0
 lock_acquire+0x115/0x350
 fs_reclaim_acquire+0x71/0x100
 prepare_alloc_pages+0x149/0x600
 __alloc_frozen_pages_noprof+0x185/0x5a0
 alloc_pages_mpol+0x21e/0x390
 alloc_pages_noprof+0xb1/0x2b0
 __pud_alloc+0x3a/0x460
 huge_pte_alloc+0x4f6/0x630
 hugetlb_fault+0x412/0x1440
 handle_mm_fault+0x24fc/0x3750
 do_user_addr_fault+0xa4f/0x1340
 exc_page_fault+0x6a/0xc0
 asm_exc_page_fault+0x26/0x30
RIP: 0033:0x7f525ed6efd8
Code: 10 8a 0e 74 0a 0f b7 74 16 fe 66 89 74 17 fe 88 0f c3 8b 4c 16 fc 8b 36 89 4c 17 fc 89 37 c3 0f 1f 00 48 8b 4c 16 f8 48 8b 36 <48> 89 37 48 89 4c 17 f8 c3 0f 10 54 16 f0 0f 10 5c 16 e0 0f 11 07
RSP: 002b:00007ffe92988388 EFLAGS: 00010206
RAX: 0000200000000540 RBX: 0000000000000004 RCX: 0a00000004000000
RDX: 000000000000000d RSI: 0000000400000003 RDI: 0000200000000540
RBP: fffffffffffffffe R08: 0000001b31720000 R09: 000000000000001a
R10: 000000000000000d R11: 0000000000000000 R12: 00007ffe929884b0
R13: 00007f525f025fac R14: 000000000011f42a R15: 00007f525f025fa0
 </TASK>
