EXT4-fs (loop4): VFS: Can't find ext4 filesystem
BUG: unable to handle kernel paging request at ffff8881c5a79000
PGD be01067 P4D be01067 PUD 1d9bf1063 PMD 80000001c5a001e3 
Oops: 000b [#1] PREEMPT SMP KASAN
CPU: 1 PID: 31075 Comm: syz-executor5 Not tainted 4.20.0-rc2+ #114
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__update_clear_spte_fast include/linux/compiler.h:209 [inline]
RIP: 0010:mmu_spte_clear_no_track arch/x86/kvm/mmu.c:819 [inline]
RIP: 0010:drop_parent_pte arch/x86/kvm/mmu.c:2004 [inline]
RIP: 0010:mmu_page_zap_pte+0x29e/0x3a0 arch/x86/kvm/mmu.c:2582
Code: 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c7 85 58 ff ff ff 00 00 00 00 48 c1 ea 03 80 3c 02 00 0f 85 d4 00 00 00 48 c1 eb 03 <49> c7 45 00 00 00 00 00 48 b8 00 00 00 00 00 fc ff df 41 be 01 00
kobject: 'loop1' (00000000efc653a4): kobject_uevent_env
RSP: 0018:ffff88817c547158 EFLAGS: 00010a06
RAX: dffffc0000000000 RBX: 1ffff1102f8a8e30 RCX: ffffffff8111497b
RDX: 1ffff11038b4f200 RSI: ffffffff81114a5b RDI: 0000000000000007
RBP: ffff88817c547228 R08: ffff8881be0e45c0 R09: ffffed103b5e5b67
R10: ffffed103b5e5b67 R11: ffff8881daf2db3b R12: 1ffff1102f8a8e2c
R13: ffff8881c5a79000 R14: 0000000000000004 R15: 0000000000000000
FS:  00000000029c3940(0000) GS:ffff8881daf00000(0000) knlGS:0000000000000000
kobject: 'loop1' (00000000efc653a4): fill_kobj_path: path = '/devices/virtual/block/loop1'
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff8881c5a79000 CR3: 00000001c0100000 CR4: 00000000001426e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
kobject: 'loop2' (00000000a8575b7d): kobject_uevent_env
kobject: 'loop2' (00000000a8575b7d): fill_kobj_path: path = '/devices/virtual/block/loop2'
 kvm_mmu_page_unlink_children arch/x86/kvm/mmu.c:2599 [inline]
 kvm_mmu_prepare_zap_page+0x215/0x1850 arch/x86/kvm/mmu.c:2643
------------[ cut here ]------------
downgrading a read lock
WARNING: CPU: 0 PID: 31127 at kernel/locking/lockdep.c:3556 __lock_downgrade kernel/locking/lockdep.c:3556 [inline]
WARNING: CPU: 0 PID: 31127 at kernel/locking/lockdep.c:3556 lock_downgrade+0x4d7/0x900 kernel/locking/lockdep.c:3819