f2fs_msg: 18 callbacks suppressed
F2FS-fs (nbd1): Unable to read 1th superblock
block nbd1: Attempted send on invalid socket
print_req_error: I/O error, dev nbd1, sector 8
F2FS-fs (nbd1): Unable to read 2th superblock
BUG: unable to handle kernel NULL pointer dereference at           (null)
IP:           (null)
PGD 7cd83067 P4D 7cd83067 PUD 2a081067 PMD 0 
Oops: 0010 [#1] PREEMPT SMP KASAN
Modules linked in:
block nbd1: Attempted send on invalid socket
CPU: 1 PID: 5428 Comm: kworker/1:0 Not tainted 4.14.210-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: pencrypt padata_serial_worker
print_req_error: I/O error, dev nbd1, sector 0
task: ffff8880257124c0 task.stack: ffff88809c790000
RIP: 0010:          (null)
RSP: 0018:ffff88809c797cd0 EFLAGS: 00010296
RAX: 0000000000000000 RBX: ffff88805efd9490 RCX: 1ffff110138f2fa2
RDX: 1ffff1100bdfb28a RSI: 0000000000000000 RDI: ffff88805efd9440
RBP: dffffc0000000000 R08: ffffe8ffffd24560 R09: 0000000000000002
R10: 0000000000000000 R11: ffff8880257124c0 R12: 0000000000000001
R13: ffff88809c797d10 R14: ffff8880b0fe7f00 R15: ffff88805efd9498
FS:  0000000000000000(0000) GS:ffff8880ba500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
F2FS-fs (nbd1): Unable to read 1th superblock
CR2: 0000000000000000 CR3: 0000000068a76000 CR4: 00000000001426e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 padata_serial_worker+0x232/0x3e0 kernel/padata.c:307
block nbd1: Attempted send on invalid socket
 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
print_req_error: I/O error, dev nbd1, sector 8
F2FS-fs (nbd1): Unable to read 2th superblock
 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
 kthread+0x30d/0x420 kernel/kthread.c:232
block nbd1: Attempted send on invalid socket
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Code: 
print_req_error: I/O error, dev nbd1, sector 0
 Bad RIP value.
F2FS-fs (nbd1): Unable to read 1th superblock
RIP:           (null) RSP: ffff88809c797cd0
CR2: 0000000000000000
---[ end trace e81fa914b8350cbf ]---
block nbd1: Attempted send on invalid socket