VFS: Found a V7 FS (block size = 512) on device loop2
sysv_free_inode: inode 0,1,2 or nonexistent inode
------------[ cut here ]------------
WARNING: CPU: 1 PID: 21208 at fs/inode.c:343 inc_nlink.cold+0x11/0x18 fs/inode.c:343
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 21208 Comm: syz-executor.2 Not tainted 4.19.188-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
 panic+0x26a/0x50e kernel/panic.c:186
 __warn.cold+0x20/0x5a kernel/panic.c:541
 report_bug+0x262/0x2b0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 fixup_bug arch/x86/kernel/traps.c:173 [inline]
 do_error_trap+0x1d7/0x310 arch/x86/kernel/traps.c:296
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1038
RIP: 0010:inc_nlink.cold+0x11/0x18 fs/inode.c:343
Code: c0 74 04 3c 03 7e 08 8b 5d 48 e9 a6 89 b5 f9 4c 89 e7 e8 a9 bd a4 f9 eb ee e8 f2 fc 6e f9 48 c7 c7 40 aa 74 88 e8 eb ee fe ff <0f> 0b e9 e8 8a b5 f9 e8 da fc 6e f9 48 8d 7b 40 b8 ff ff 37 00 48
RSP: 0018:ffff8880433bfdf0 EFLAGS: 00010282
RAX: 0000000000000024 RBX: ffff88803213a238 RCX: 0000000000000000
RDX: 000000000000c623 RSI: ffffffff814dddb1 RDI: ffffed1008677fb0
RBP: 0000000000000000 R08: 0000000000000024 R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000000 R12: ffff88803213a280
R13: ffff88808dc1e720 R14: 000000000000007e R15: 0000000000000004
 inode_inc_link_count include/linux/fs.h:2101 [inline]
 sysv_mkdir+0x21/0x150 fs/sysv/namei.c:131
 vfs_mkdir+0x508/0x7a0 fs/namei.c:3819
 do_mkdirat+0x262/0x2d0 fs/namei.c:3842
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x466459
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f534b04f188 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000466459
RDX: 0000000000000004 RSI: 00000000200000c0 RDI: 0000000000000006
RBP: 00000000004bfb23 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007fffb391a99f R14: 00007f534b04f300 R15: 0000000000022000
Kernel Offset: disabled
Rebooting in 86400 seconds..