======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G S           L     
------------------------------------------------------
syz.2.9594/32724 is trying to acquire lock:
ffffffff8ee90160 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:316 [inline]
ffffffff8ee90160 (fs_reclaim){+.+.}-{0:0}, at: prepare_alloc_pages+0x149/0x600 mm/page_alloc.c:5113

but task is already holding lock:
ffff88804d3069b8 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:619 [inline]
ffff88804d3069b8 (&mm->mmap_lock){++++}-{4:4}, at: get_mmap_lock_carefully mm/mmap_lock.c:441 [inline]
ffff88804d3069b8 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x36/0x340 mm/mmap_lock.c:501

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #7 (&mm->mmap_lock){++++}-{4:4}:
       __might_fault+0xcb/0x130 mm/memory.c:7482
       _copy_from_iter+0x100/0x1660 lib/iov_iter.c:271
       copy_from_iter include/linux/uio.h:228 [inline]
       copy_from_iter_full include/linux/uio.h:245 [inline]
       skb_do_copy_data_nocache include/net/sock.h:2327 [inline]
       skb_copy_to_page_nocache include/net/sock.h:2353 [inline]
       tcp_sendmsg_locked+0x20cf/0x5400 net/ipv4/tcp.c:1310
       tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1451
       sock_sendmsg_nosec+0x10e/0x180 net/socket.c:801
       __sock_sendmsg net/socket.c:815 [inline]
       sock_write_iter+0x2de/0x3e0 net/socket.c:1266
       new_sync_write fs/read_write.c:595 [inline]
       vfs_write+0x612/0xba0 fs/read_write.c:687
       ksys_write+0x150/0x270 fs/read_write.c:739
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (sk_lock-AF_INET){+.+.}-{0:0}:
       lock_sock_nested+0x41/0x100 net/core/sock.c:3830
       lock_sock include/net/sock.h:1713 [inline]
       inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:913
       nbd_mark_nsock_dead+0x2cb/0x550 drivers/block/nbd.c:319
       recv_work+0x1cee/0x1e10 drivers/block/nbd.c:1030
       process_one_work kernel/workqueue.c:3396 [inline]
       process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
       worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
       kthread+0x38b/0x480 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       nbd_handle_cmd drivers/block/nbd.c:1143 [inline]
       nbd_queue_rq+0x373/0xff0 drivers/block/nbd.c:1207
       blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xd36/0x1580 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
       blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2532
       process_one_work kernel/workqueue.c:3396 [inline]
       process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
       worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
       kthread+0x38b/0x480 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #4 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       nbd_queue_rq+0xc1/0xff0 drivers/block/nbd.c:1199
       blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xd36/0x1580 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
       blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2532
       process_one_work kernel/workqueue.c:3396 [inline]
       process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
       worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
       kthread+0x38b/0x480 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #3 (set->srcu){.+.+}-{0:0}:
       srcu_lock_sync include/linux/srcu.h:210 [inline]
       __synchronize_srcu+0xc9/0x2f0 kernel/rcu/srcutree.c:1462
       elevator_switch+0x1e8/0x7b0 block/elevator.c:576
       elevator_change+0x2fa/0x480 block/elevator.c:681
       elevator_set_default+0x375/0x440 block/elevator.c:754
       blk_register_queue+0x3f3/0x4e0 block/blk-sysfs.c:992
       __add_disk+0x6b8/0xdb0 block/genhd.c:531
       add_disk_fwnode+0x100/0x3a0 block/genhd.c:600
       add_disk include/linux/blkdev.h:798 [inline]
       nbd_dev_add+0x733/0xb60 drivers/block/nbd.c:2026
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2743
       do_one_initcall+0x250/0x870 init/main.c:1362
       do_initcall_level+0x10a/0x1a0 init/main.c:1424
       do_initcalls+0x59/0xa0 init/main.c:1440
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1675
       kernel_init+0x22/0x1d0 init/main.c:1565
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (&q->elevator_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       queue_requests_store+0x45b/0x5f0 block/blk-sysfs.c:124
       queue_attr_store+0x207/0x2b0 block/blk-sysfs.c:906
       kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
       do_iter_readv_writev+0x612/0x8c0 fs/read_write.c:-1
       vfs_writev+0x343/0x990 fs/read_write.c:1058
       do_writev+0x154/0x2e0 fs/read_write.c:1104
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&q->q_usage_counter(io)#66){++++}-{0:0}:
       blk_alloc_queue+0x544/0x690 block/blk-core.c:504
       blk_mq_alloc_queue block/blk-mq.c:4420 [inline]
       __blk_mq_alloc_disk+0x194/0x390 block/blk-mq.c:4467
       null_add_dev+0xe82/0x1d70 drivers/block/null_blk/main.c:2017
       null_create_dev drivers/block/null_blk/main.c:2114 [inline]
       null_init+0x1e3/0x390 drivers/block/null_blk/main.c:2178
       do_one_initcall+0x250/0x870 init/main.c:1362
       do_initcall_level+0x10a/0x1a0 init/main.c:1424
       do_initcalls+0x59/0xa0 init/main.c:1440
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1675
       kernel_init+0x22/0x1d0 init/main.c:1565
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 (fs_reclaim){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3209 [inline]
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
       lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
       __fs_reclaim_acquire mm/page_alloc.c:4375 [inline]
       fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4389
       might_alloc include/linux/sched/mm.h:316 [inline]
       prepare_alloc_pages+0x149/0x600 mm/page_alloc.c:5113
       __alloc_frozen_pages_noprof+0x185/0x5a0 mm/page_alloc.c:5421
       alloc_pages_mpol+0x21e/0x390 mm/mempolicy.c:2486
       folio_alloc_mpol_noprof+0x39/0x160 mm/mempolicy.c:2505
       vma_alloc_folio_noprof+0xe1/0x1e0 mm/mempolicy.c:2540
       folio_prealloc mm/memory.c:-1 [inline]
       alloc_anon_folio mm/memory.c:5387 [inline]
       do_anonymous_page mm/memory.c:5482 [inline]
       do_pte_missing+0x173a/0x34b0 mm/memory.c:4698
       handle_pte_fault mm/memory.c:6558 [inline]
       __handle_mm_fault mm/memory.c:6707 [inline]
       handle_mm_fault+0x1a53/0x3750 mm/memory.c:6876
       do_user_addr_fault+0x746/0x1340 arch/x86/mm/fault.c:1394
       handle_page_fault arch/x86/mm/fault.c:1483 [inline]
       exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536
       asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
       copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline]
       raw_copy_to_user arch/x86/include/asm/uaccess_64.h:147 [inline]
       _inline_copy_to_user include/linux/uaccess.h:202 [inline]
       _copy_to_user+0x85/0xb0 lib/usercopy.c:24
       copy_to_user include/linux/uaccess.h:230 [inline]
       iowarrior_read+0x7a1/0xb60 drivers/usb/misc/iowarrior.c:341
       vfs_read+0x213/0xa80 fs/read_write.c:572
       ksys_read+0x150/0x270 fs/read_write.c:716
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  fs_reclaim --> sk_lock-AF_INET --> &mm->mmap_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(&mm->mmap_lock);
                               lock(sk_lock-AF_INET);
                               lock(&mm->mmap_lock);
  lock(fs_reclaim);

 *** DEADLOCK ***

locks held by syz.2.9594/32724: 2, last CPU#0:
 #0: ffff88807ac31868 (&dev->mutex#6){+.+.}-{4:4}, at: iowarrior_read+0x109/0xb60 drivers/usb/misc/iowarrior.c:287
 #1: ffff88804d3069b8 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:619 [inline]
 #1: ffff88804d3069b8 (&mm->mmap_lock){++++}-{4:4}, at: get_mmap_lock_carefully mm/mmap_lock.c:441 [inline]
 #1: ffff88804d3069b8 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x36/0x340 mm/mmap_lock.c:501

stack backtrace:
CPU: 0 UID: 0 PID: 32724 Comm: syz.2.9594 Tainted: G S           L      syzkaller #0 PREEMPT(lazy) 
Tainted: [S]=CPU_OUT_OF_SPEC, [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087
 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219
 check_prev_add kernel/locking/lockdep.c:3209 [inline]
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
 __fs_reclaim_acquire mm/page_alloc.c:4375 [inline]
 fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4389
 might_alloc include/linux/sched/mm.h:316 [inline]
 prepare_alloc_pages+0x149/0x600 mm/page_alloc.c:5113
 __alloc_frozen_pages_noprof+0x185/0x5a0 mm/page_alloc.c:5421
 alloc_pages_mpol+0x21e/0x390 mm/mempolicy.c:2486
 folio_alloc_mpol_noprof+0x39/0x160 mm/mempolicy.c:2505
 vma_alloc_folio_noprof+0xe1/0x1e0 mm/mempolicy.c:2540
 folio_prealloc mm/memory.c:-1 [inline]
 alloc_anon_folio mm/memory.c:5387 [inline]
 do_anonymous_page mm/memory.c:5482 [inline]
 do_pte_missing+0x173a/0x34b0 mm/memory.c:4698
 handle_pte_fault mm/memory.c:6558 [inline]
 __handle_mm_fault mm/memory.c:6707 [inline]
 handle_mm_fault+0x1a53/0x3750 mm/memory.c:6876
 do_user_addr_fault+0x746/0x1340 arch/x86/mm/fault.c:1394
 handle_page_fault arch/x86/mm/fault.c:1483 [inline]
 exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
RIP: 0010:copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline]
RIP: 0010:raw_copy_to_user arch/x86/include/asm/uaccess_64.h:147 [inline]
RIP: 0010:_inline_copy_to_user include/linux/uaccess.h:202 [inline]
RIP: 0010:_copy_to_user+0x85/0xb0 lib/usercopy.c:24
Code: e8 b0 d4 e8 fc 4d 39 fc 72 3d 4d 39 ec 77 38 e8 d1 d1 e8 fc 4c 89 f7 89 de e8 17 dc 58 fd 0f 01 cb 4c 89 ff 48 89 d9 4c 89 f6 <f3> a4 0f 1f 00 48 89 cb 0f 01 ca 48 89 d8 5b 41 5c 41 5d 41 5e 41
RSP: 0018:ffffc900041d7af0 EFLAGS: 00050256
RAX: ffffffff84df0001 RBX: 000000000000004a RCX: 000000000000004a
RDX: 0000000000000000 RSI: ffff88802998c000 RDI: 0000200000000480
RBP: ffffc900041d7c90 R08: ffff88802998c049 R09: 1ffff11005331809
R10: dffffc0000000000 R11: ffffed100533180a R12: 00002000000004ca
R13: 00007ffffffff000 R14: ffff88802998c000 R15: 0000200000000480
 copy_to_user include/linux/uaccess.h:230 [inline]
 iowarrior_read+0x7a1/0xb60 drivers/usb/misc/iowarrior.c:341
 vfs_read+0x213/0xa80 fs/read_write.c:572
 ksys_read+0x150/0x270 fs/read_write.c:716
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1726d9e159
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:00007f1727d02028 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f1727025fa0 RCX: 00007f1726d9e159
RDX: 000000000000004a RSI: 0000200000000480 RDI: 0000000000000004
RBP: 00007f1726e3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1727026038 R14: 00007f1727025fa0 R15: 00007ffefba8f9d8
 </TASK>
----------------
Code disassembly (best guess):
   0:	e8 b0 d4 e8 fc       	call   0xfce8d4b5
   5:	4d 39 fc             	cmp    %r15,%r12
   8:	72 3d                	jb     0x47
   a:	4d 39 ec             	cmp    %r13,%r12
   d:	77 38                	ja     0x47
   f:	e8 d1 d1 e8 fc       	call   0xfce8d1e5
  14:	4c 89 f7             	mov    %r14,%rdi
  17:	89 de                	mov    %ebx,%esi
  19:	e8 17 dc 58 fd       	call   0xfd58dc35
  1e:	0f 01 cb             	stac
  21:	4c 89 ff             	mov    %r15,%rdi
  24:	48 89 d9             	mov    %rbx,%rcx
  27:	4c 89 f6             	mov    %r14,%rsi
* 2a:	f3 a4                	rep movsb %ds:(%rsi),%es:(%rdi) <-- trapping instruction
  2c:	0f 1f 00             	nopl   (%rax)
  2f:	48 89 cb             	mov    %rcx,%rbx
  32:	0f 01 ca             	clac
  35:	48 89 d8             	mov    %rbx,%rax
  38:	5b                   	pop    %rbx
  39:	41 5c                	pop    %r12
  3b:	41 5d                	pop    %r13
  3d:	41 5e                	pop    %r14
  3f:	41                   	rex.B