------------[ cut here ]------------
!rwb
WARNING: block/blk-wbt.c:785 at wbt_init_enable_default+0x164/0x1c0 block/blk-wbt.c:785, CPU#2: syz.3.3706/21597
Modules linked in:
CPU: 2 UID: 0 PID: 21597 Comm: syz.3.3706 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:wbt_init_enable_default+0x164/0x1c0 block/blk-wbt.c:785
Code: b5 21 fd 5b 5d 41 5c 41 5d 41 5e c3 cc cc cc cc 4c 89 f7 e8 0e 51 8d fd eb 83 4c 89 f7 e8 04 51 8d fd eb d0 e8 ed b4 21 fd 90 <0f> 0b 90 e9 e9 fe ff ff e8 df b4 21 fd 90 0f 0b 90 48 b8 00 00 00
RSP: 0018:ffffc9000ed77b38 EFLAGS: 00010287
RAX: 000000000001291b RBX: ffff888026e39000 RCX: ffffc9000db93000
RDX: 0000000000080000 RSI: ffffffff84e68e93 RDI: ffffffff8c1b1e20
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff888027c068d8
R13: ffff88802968802c R14: ffff888026e39390 R15: ffff888027c068e8
FS:  0000000000000000(0000) GS:ffff888097340000(0063) knlGS:00000000f5464b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f516cf30 CR3: 000000002adbe000 CR4: 0000000000352ef0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000002
DR3: ffffffffefffff15 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 blk_register_queue+0x42c/0x590 block/blk-sysfs.c:949
 __add_disk+0x73f/0xe40 block/genhd.c:528
 add_disk_fwnode+0x118/0x5c0 block/genhd.c:597
 add_disk include/linux/blkdev.h:785 [inline]
 loop_add+0x90b/0xb60 drivers/block/loop.c:2092
 loop_control_get_free drivers/block/loop.c:2208 [inline]
 loop_control_ioctl+0x1fa/0x620 drivers/block/loop.c:2223
 __do_compat_sys_ioctl fs/ioctl.c:695 [inline]
 __se_compat_sys_ioctl fs/ioctl.c:638 [inline]
 __ia32_compat_sys_ioctl+0x2cf/0x360 fs/ioctl.c:638
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xe3/0x8c0 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf7fe8f6c
Code: d2 74 05 c1 e8 0c 89 02 8b 5d fc 31 c0 c9 c3 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 2e 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00 58 b8
RSP: 002b:00000000f546450c EFLAGS: 00000292 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 0000000000004c82
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
----------------
Code disassembly (best guess):
   0:	d2 74 05 c1          	shlb   %cl,-0x3f(%rbp,%rax,1)
   4:	e8 0c 89 02 8b       	call   0x8b028915
   9:	5d                   	pop    %rbp
   a:	fc                   	cld
   b:	31 c0                	xor    %eax,%eax
   d:	c9                   	leave
   e:	c3                   	ret
   f:	90                   	nop
  10:	90                   	nop
  11:	90                   	nop
  12:	90                   	nop
  13:	90                   	nop
  14:	90                   	nop
  15:	90                   	nop
  16:	90                   	nop
  17:	90                   	nop
  18:	90                   	nop
  19:	90                   	nop
  1a:	90                   	nop
  1b:	90                   	nop
  1c:	90                   	nop
  1d:	90                   	nop
  1e:	0f 1f 00             	nopl   (%rax)
  21:	51                   	push   %rcx
  22:	52                   	push   %rdx
  23:	55                   	push   %rbp
  24:	89 e5                	mov    %esp,%ebp
  26:	0f 34                	sysenter
  28:	cd 80                	int    $0x80
* 2a:	5d                   	pop    %rbp <-- trapping instruction
  2b:	5a                   	pop    %rdx
  2c:	59                   	pop    %rcx
  2d:	c3                   	ret
  2e:	90                   	nop
  2f:	2e 8d b4 26 00 00 00 	cs lea 0x0(%rsi,%riz,1),%esi
  36:	00
  37:	8d b4 26 00 00 00 00 	lea    0x0(%rsi,%riz,1),%esi
  3e:	58                   	pop    %rax
  3f:	b8                   	.byte 0xb8