RAX: ffffffffffffffda RBX: 00007f618c2bcc90 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f618c2bd6d4
R13: 00000000004c3106 R14: 00000000004d6808 R15: 0000000000000005
BUG: unable to handle kernel NULL pointer dereference at 0000000000000120
kobject: 'loop4' (ffff8880a4afb360): kobject_uevent_env
IP: set_bit arch/x86/include/asm/bitops.h:81 [inline]
IP: cpumask_set_cpu include/linux/cpumask.h:283 [inline]
IP: blk_mq_map_swqueue+0x25e/0x9c0 block/blk-mq.c:2171
PGD a4080067 P4D a4080067 PUD 5ff06067 PMD 0 
kobject: 'loop4' (ffff8880a4afb360): fill_kobj_path: path = '/devices/virtual/block/loop4'
Oops: 0002 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 10463 Comm: syz-executor.1 Not tainted 4.14.138 #34
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff88805c440640 task.stack: ffff88805ded8000
RIP: 0010:set_bit arch/x86/include/asm/bitops.h:81 [inline]
RIP: 0010:cpumask_set_cpu include/linux/cpumask.h:283 [inline]
RIP: 0010:blk_mq_map_swqueue+0x25e/0x9c0 block/blk-mq.c:2171
RSP: 0018:ffff88805dedfa50 EFLAGS: 00010246
RAX: 0000000000040000 RBX: 0000000000000001 RCX: ffffc90009a5b000
RDX: 0000000000000000 RSI: ffffffff82c9fafa RDI: ffff8880a491e608
RBP: ffff88805dedfac8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffff88805dedf8e8 R12: 0000000000000001
R13: ffff8880a4fa1340 R14: dffffc0000000000 R15: ffff8880a403a440
FS:  00007f618c2bd700(0000) GS:ffff8880aee00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000120 CR3: 00000000908c4000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 blk_mq_queue_reinit block/blk-mq.c:2514 [inline]
 __blk_mq_update_nr_hw_queues block/blk-mq.c:2748 [inline]
 blk_mq_update_nr_hw_queues+0x21c/0x3a0 block/blk-mq.c:2758
 nbd_start_device+0x12c/0xb00 drivers/block/nbd.c:1144
 nbd_start_device_ioctl drivers/block/nbd.c:1185 [inline]
 __nbd_ioctl drivers/block/nbd.c:1256 [inline]
 nbd_ioctl+0x43d/0xae0 drivers/block/nbd.c:1296
 __blkdev_driver_ioctl block/ioctl.c:297 [inline]
 blkdev_ioctl+0x96b/0x1860 block/ioctl.c:594
 block_ioctl+0xde/0x120 fs/block_dev.c:1881
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x7ae/0x1060 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x459829
RSP: 002b:00007f618c2bcc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f618c2bcc90 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f618c2bd6d4
R13: 00000000004c3106 R14: 00000000004d6808 R15: 0000000000000005
Code: ea 03 42 80 3c 32 00 0f 85 94 06 00 00 41 83 fc 3f 48 8b 17 0f 87 4b 04 00 00 48 89 55 c8 48 89 45 d0 e8 76 e2 92 fe 48 8b 55 c8 <f0> 48 0f ab 9a 20 01 00 00 48 8d ba 78 01 00 00 48 8b 45 d0 48 
RIP: set_bit arch/x86/include/asm/bitops.h:81 [inline] RSP: ffff88805dedfa50
RIP: cpumask_set_cpu include/linux/cpumask.h:283 [inline] RSP: ffff88805dedfa50
RIP: blk_mq_map_swqueue+0x25e/0x9c0 block/blk-mq.c:2171 RSP: ffff88805dedfa50
CR2: 0000000000000120
---[ end trace f26eec0b69fb2a02 ]---
kobject: 'loop0' (ffff8880a49c06e0): kobject_uevent_env