RAX: ffffffffffffffda RBX: 00007f135893c6d4 RCX: 000000000045c479
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000007
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000008
R13: 0000000000000402 R14: 00000000004c65f9 R15: 0000000000000009
BUG: unable to handle kernel NULL pointer dereference at 0000000000000120
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+0x253/0x9b0 block/blk-mq.c:2171
PGD 8e8c8067 P4D 8e8c8067 PUD 8c70d067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 17749 Comm: syz-executor.2 Not tainted 4.14.172-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8880949e8140 task.stack: ffff888049dc8000
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+0x253/0x9b0 block/blk-mq.c:2171
RSP: 0018:ffff888049dcfa98 EFLAGS: 00010246
RAX: 0000000000040000 RBX: ffff8880a3e64ff0 RCX: ffffc9000ba52000
RDX: 0000000000040000 RSI: ffffffff82efbdd3 RDI: ffffffff87a0bd68
RBP: 0000000000000001 R08: ffff8880a3cd5180 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
R13: ffff88821884ecc0 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007f135893c700(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000120 CR3: 0000000081636000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 blk_mq_queue_reinit block/blk-mq.c:2512 [inline]
 __blk_mq_update_nr_hw_queues block/blk-mq.c:2746 [inline]
 blk_mq_update_nr_hw_queues+0x211/0x390 block/blk-mq.c:2756
 nbd_start_device+0x1d7/0xcb0 drivers/block/nbd.c:1187
 nbd_start_device_ioctl drivers/block/nbd.c:1238 [inline]
 __nbd_ioctl drivers/block/nbd.c:1320 [inline]
 nbd_ioctl+0x3e8/0xa30 drivers/block/nbd.c:1360
 __blkdev_driver_ioctl block/ioctl.c:297 [inline]
 blkdev_ioctl+0x91d/0x17d0 block/ioctl.c:594
 block_ioctl+0xd9/0x120 fs/block_dev.c:1881
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xfe0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c479
RSP: 002b:00007f135893bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f135893c6d4 RCX: 000000000045c479
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000007
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000008
R13: 0000000000000402 R14: 00000000004c65f9 R15: 0000000000000009
Code: 4d 8d 34 c8 4c 89 f1 48 c1 e9 03 42 80 3c 39 00 0f 85 7d 06 00 00 83 fd 3f 4d 8b 36 0f 87 42 04 00 00 48 89 04 24 e8 5d 87 6a fe <f0> 4d 0f ab a6 20 01 00 00 49 8d be 78 01 00 00 48 8b 04 24 48 
RIP: set_bit arch/x86/include/asm/bitops.h:81 [inline] RSP: ffff888049dcfa98
RIP: cpumask_set_cpu include/linux/cpumask.h:283 [inline] RSP: ffff888049dcfa98
RIP: blk_mq_map_swqueue+0x253/0x9b0 block/blk-mq.c:2171 RSP: ffff888049dcfa98
CR2: 0000000000000120
---[ end trace f7065c9f22c3e19f ]---