======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.6177/20123 is trying to acquire lock:
ffffffff8ec848a0 (fs_reclaim){+.+.}-{0:0}, at: prepare_alloc_pages+0x15b/0x650

but task is already holding lock:
ffff888029817870 (&vma_lock->rw_sema){++++}-{4:4}, at: hugetlb_fault+0x3dd/0x12c0

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #9 (&vma_lock->rw_sema){++++}-{4:4}:
       down_write+0x96/0x200
       __hugetlb_zap_begin+0x259/0x2d0
       unmap_vmas+0x36b/0x550
       unmap_region+0x208/0x330
       mmap_region+0xc62/0x2310
       do_mmap+0xc3b/0x10c0
       vm_mmap_pgoff+0x272/0x4e0
       ksys_mmap_pgoff+0x57d/0x760
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #8 (&mm->mmap_lock){++++}-{4:4}:
       __might_fault+0xcb/0x130
       _copy_from_user+0x28/0xb0
       csum_and_copy_from_iter_full+0x210/0x1fb0
       ip_generic_getfrag+0x149/0x2d0
       __ip6_append_data+0x3b26/0x40c0
       ip6_append_data+0x108/0x270
       rawv6_sendmsg+0x1298/0x18c0
       sock_sendmsg_nosec+0x10e/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

-> #7 (sk_lock-AF_INET6){+.+.}-{0:0}:
       lock_sock_nested+0x41/0x100
       tls_sw_sendmsg+0x161/0x2860
       sock_sendmsg_nosec+0x90/0x180
       sock_write_iter+0x2de/0x3e0
       do_iter_readv_writev+0x612/0x8c0
       vfs_writev+0x343/0x990
       do_writev+0x154/0x2e0
       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+0x100/0x3a0
       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)#50){++++}-{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
       prepare_alloc_pages+0x15b/0x650
       __alloc_frozen_pages_noprof+0x12f/0x380
       alloc_pages_mpol+0x212/0x380
       alloc_pages_noprof+0xac/0x2a0
       __pud_alloc+0x3a/0x460
       huge_pte_alloc+0x4f6/0x630
       hugetlb_fault+0x42e/0x12c0
       handle_mm_fault+0x1f42/0x3080
       do_user_addr_fault+0xa4d/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 --> &mm->mmap_lock --> &vma_lock->rw_sema

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(&vma_lock->rw_sema);
                               lock(&mm->mmap_lock);
                               lock(&vma_lock->rw_sema);
  lock(fs_reclaim);

 *** DEADLOCK ***

3 locks held by syz.0.6177/20123:
 #0: ffff888113504508 (vm_lock){++++}-{0:0}, at: lock_vma_under_rcu+0x1d1/0x500
 #1: ffff888103a8c280 (&hugetlb_fault_mutex_table[i]){+.+.}-{4:4}, at: hugetlb_fault+0x3d0/0x12c0
 #2: ffff888029817870 (&vma_lock->rw_sema){++++}-{4:4}, at: hugetlb_fault+0x3dd/0x12c0

stack backtrace:
CPU: 0 UID: 0 PID: 20123 Comm: syz.0.6177 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
 prepare_alloc_pages+0x15b/0x650
 __alloc_frozen_pages_noprof+0x12f/0x380
 alloc_pages_mpol+0x212/0x380
 alloc_pages_noprof+0xac/0x2a0
 __pud_alloc+0x3a/0x460
 huge_pte_alloc+0x4f6/0x630
 hugetlb_fault+0x42e/0x12c0
 handle_mm_fault+0x1f42/0x3080
 do_user_addr_fault+0xa4d/0x1340
 exc_page_fault+0x6a/0xc0
 asm_exc_page_fault+0x26/0x30
RIP: 0033:0x7efddba67682
Code: 30 48 8b 14 24 48 85 d2 74 17 8b 44 24 10 0f c8 89 c0 48 89 44 24 10 48 83 fa 01 0f 85 aa 02 00 00 48 8b 44 24 18 8b 74 24 10 <89> 30 e9 1e fe ff ff 48 8b 44 24 18 8b 10 48 8b 04 24 48 85 c0 0f
RSP: 002b:00007fff48cf9fa0 EFLAGS: 00010246
RAX: 0000200000000180 RBX: 0000000000000004 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000011 RDI: 000055556e2203d8
RBP: 00007fff48cfa0c0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000011 R11: 0000000000000000 R12: 00007fff48cfa100
R13: 00007efddbe25fac R14: 00000000000619c1 R15: 00007efddbe25fa0
 </TASK>
