VFS: Found a V7 FS (block size = 512) on device loop4
sysv_free_inode: inode 0,1,2 or nonexistent inode
VFS: Found a V7 FS (block size = 512) on device loop4
------------[ cut here ]------------
WARNING: CPU: 0 PID: 12887 at fs/inode.c:342 inc_nlink+0x113/0x130 fs/inode.c:342
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 12887 Comm: syz-executor.4 Not tainted 4.14.206-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 panic+0x1f9/0x42d kernel/panic.c:183
 __warn.cold+0x20/0x4b kernel/panic.c:547
 report_bug+0x208/0x249 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:177 [inline]
 fixup_bug arch/x86/kernel/traps.c:172 [inline]
 do_error_trap+0x195/0x2d0 arch/x86/kernel/traps.c:295
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:964
RIP: 0010:inc_nlink+0x113/0x130 fs/inode.c:342
RSP: 0018:ffff888046887df0 EFLAGS: 00010212
RAX: 0000000000040000 RBX: ffff8880523391f8 RCX: ffffc9000b6df000
RDX: 0000000000000a14 RSI: ffffffff818eb7a3 RDI: ffff8880523392d0
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888052339240
R13: ffff88808eabb000 R14: ffffffff87aa2dc0 R15: 0000000000000000
 inode_inc_link_count include/linux/fs.h:2039 [inline]
 sysv_mkdir+0x21/0x120 fs/sysv/namei.c:136
 vfs_mkdir+0x463/0x6e0 fs/namei.c:3849
 SYSC_mkdirat fs/namei.c:3872 [inline]
 SyS_mkdirat+0x1fd/0x270 fs/namei.c:3856
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45deb9
RSP: 002b:00007fe9ddc9ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 0000000000021040 RCX: 000000000045deb9
RDX: 000000000000000a RSI: 00000000200001c0 RDI: 0000000000000005
RBP: 000000000118bf60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007fffbd83077f R14: 00007fe9ddc9f9c0 R15: 000000000118bf2c
Kernel Offset: disabled
Rebooting in 86400 seconds..