BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD af57c067 P4D af57c067 PUD af57b067 PMD 0 
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 16149 Comm: syz-executor.5 Not tainted 5.14.0-rc6-next-20210820-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc90014bc7c20 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffffffff8d282060 RCX: 0000000000000000
RDX: 1ffffffff1a50422 RSI: ffffffff87d5bbfd RDI: ffff88809c333640
RBP: ffff88809c333640 R08: 0000000000000000 R09: 0000000000000001
R10: ffffffff87d5bb78 R11: 0000000000000001 R12: 0000000000000003
R13: ffff88809c333c58 R14: ffff88809c333498 R15: ffff88809c3336c0
FS:  0000000001a9d400(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000000af57d000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 unix_shutdown+0x292/0x5c0 net/unix/af_unix.c:2857
 nbd_mark_nsock_dead+0xb2/0x5a0 drivers/block/nbd.c:307
 sock_shutdown+0x16d/0x200 drivers/block/nbd.c:386
 nbd_clear_sock drivers/block/nbd.c:1239 [inline]
 nbd_config_put+0x1bb/0x9d0 drivers/block/nbd.c:1261
 nbd_release+0x112/0x170 drivers/block/nbd.c:1551
 blkdev_put_whole fs/block_dev.c:1102 [inline]
 blkdev_put+0x2fb/0x9e0 fs/block_dev.c:1393
 blkdev_close+0x90/0xc0 fs/block_dev.c:1403
 __fput+0x288/0x9f0 fs/file_table.c:280
 task_work_run+0xdd/0x1a0 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
 do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4193fb
Code: 0f 05 48 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8 63 fc ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 a1 fc ff ff 8b 44
RSP: 002b:00007fffd533db20 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000008 RCX: 00000000004193fb
RDX: 0000000000570a00 RSI: ffffffff893629f8 RDI: 0000000000000007
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000001b30a22ce8
R10: 00000000000009d2 R11: 0000000000000293 R12: 0000000000060215
R13: 00000000000003e8 R14: 000000000056bf80 R15: 0000000000060139
Modules linked in:
CR2: 0000000000000000
---[ end trace ad740989a8d6c971 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc90014bc7c20 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffffffff8d282060 RCX: 0000000000000000
RDX: 1ffffffff1a50422 RSI: ffffffff87d5bbfd RDI: ffff88809c333640
RBP: ffff88809c333640 R08: 0000000000000000 R09: 0000000000000001
R10: ffffffff87d5bb78 R11: 0000000000000001 R12: 0000000000000003
R13: ffff88809c333c58 R14: ffff88809c333498 R15: ffff88809c3336c0
FS:  0000000001a9d400(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000000af57d000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400