------------[ cut here ]------------
WARNING: CPU: 1 PID: 31514 at lib/percpu-refcount.c:111 percpu_ref_exit+0xab/0xd0 lib/percpu-refcount.c:111
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 31514 Comm: syz-executor.0 Not tainted 5.5.0-rc2-next-20191220-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+0x197/0x210 lib/dump_stack.c:118
 panic+0x2e3/0x75c kernel/panic.c:221
 __warn.cold+0x2f/0x3e kernel/panic.c:582
 report_bug+0x289/0x300 lib/bug.c:195
 fixup_bug arch/x86/kernel/traps.c:174 [inline]
 fixup_bug arch/x86/kernel/traps.c:169 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:267
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:286
 invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:percpu_ref_exit+0xab/0xd0 lib/percpu-refcount.c:111
Code: 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 75 1d 48 c7 43 08 03 00 00 00 e8 01 41 e5 fd 5b 41 5c 41 5d 5d c3 e8 f5 40 e5 fd <0f> 0b eb bf 4c 89 ef e8 29 2c 23 fe eb d9 e8 82 2b 23 fe eb a7 4c
RSP: 0018:ffffc9001cc3fd10 EFLAGS: 00010293
RAX: ffff88809aa68480 RBX: ffff8880924ff810 RCX: ffffffff83901432
RDX: 0000000000000000 RSI: ffffffff8390149b RDI: ffff8880924ff828
RBP: ffffc9001cc3fd28 R08: ffff88809aa68480 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000607f5147b2f0
R13: ffff8880924ff818 R14: ffff88809009c800 R15: ffff88809009ca28
 io_sqe_files_unregister+0x7d/0x2f0 fs/io_uring.c:4623
 io_ring_ctx_free fs/io_uring.c:5575 [inline]
 io_ring_ctx_wait_and_kill+0x430/0x9a0 fs/io_uring.c:5644
 io_uring_release+0x42/0x50 fs/io_uring.c:5652
 __fput+0x2ff/0x890 fs/file_table.c:280
 ____fput+0x16/0x20 fs/file_table.c:313
 task_work_run+0x145/0x1c0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
 do_syscall_64+0x676/0x790 arch/x86/entry/common.c:304
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4144b1
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffe1025c8a0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00000000004144b1
RDX: 0000001b2c120000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000001 R08: 00000000177afe4d R09: 00000000177afe51
R10: 00007ffe1025c980 R11: 0000000000000293 R12: 000000000075c9a0
R13: 000000000075c9a0 R14: 0000000000760628 R15: 000000000075bf2c
Kernel Offset: disabled
Rebooting in 86400 seconds..