------------[ cut here ]------------
sysfs group 'loop' not found for kobject 'loop4'
WARNING: CPU: 1 PID: 20339 at fs/sysfs/group.c:237 sysfs_remove_group+0x15b/0x1b0 fs/sysfs/group.c:235
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 20339 Comm: syz-executor3 Not tainted 4.15.0-rc8-next-20180117+ #99
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+0x194/0x257 lib/dump_stack.c:53
 panic+0x1e4/0x41c kernel/panic.c:183
 __warn+0x1dc/0x200 kernel/panic.c:547
 report_bug+0x211/0x2d0 lib/bug.c:184
 fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
 fixup_bug arch/x86/kernel/traps.c:247 [inline]
 do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
 invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1096
RIP: 0010:sysfs_remove_group+0x15b/0x1b0 fs/sysfs/group.c:235
RSP: 0018:ffff8801cfa8f9a8 EFLAGS: 00010282
RAX: dffffc0000000008 RBX: ffffffff86d097c0 RCX: ffffffff815aa09e
RDX: 0000000000003567 RSI: ffffc90003cb7000 RDI: 1ffff10039f51eba
RBP: ffff8801cfa8f9d0 R08: 1ffff10039f51e7c R09: 0000000000000000
R10: ffffffff87f56180 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8801d58feee0 R14: ffffffff8609ac40 R15: ffff8801d58f39e8
 loop_sysfs_exit drivers/block/loop.c:798 [inline]
 loop_clr_fd+0x4f2/0xb50 drivers/block/loop.c:1051
 lo_ioctl+0x1307/0x1b70 drivers/block/loop.c:1365
 __blkdev_driver_ioctl block/ioctl.c:303 [inline]
 blkdev_ioctl+0x1759/0x1e00 block/ioctl.c:601
 block_ioctl+0xde/0x120 fs/block_dev.c:1859
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452e39
RSP: 002b:00007fd740246c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452e39
RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000014
RBP: 00000000000003bb R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f3a28
R13: 00000000ffffffff R14: 00007fd7402476d4 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..