==================================================================
BUG: KASAN: use-after-free in hlist_add_head include/linux/list.h:704 [inline]
BUG: KASAN: use-after-free in preempt_notifier_register+0x1ec/0x200 kernel/sched/core.c:2465
Write of size 8 at addr ffff8801ce1d8ad0 by task syz-executor5/8196

CPU: 0 PID: 8196 Comm: syz-executor5 Not tainted 4.19.0-rc4-next-20180921+ #77
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+0x1d3/0x2c4 lib/dump_stack.c:113
 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
 __asan_report_store8_noabort+0x17/0x20 mm/kasan/report.c:438
 hlist_add_head include/linux/list.h:704 [inline]
 preempt_notifier_register+0x1ec/0x200 kernel/sched/core.c:2465
 vcpu_load+0x2a/0x70 arch/x86/kvm/../../../virt/kvm/kvm_main.c:163
 vmx_free_vcpu_nested arch/x86/kvm/vmx.c:10930 [inline]
 vmx_free_vcpu+0x18d/0x300 arch/x86/kvm/vmx.c:10944
 kvm_arch_vcpu_free arch/x86/kvm/x86.c:8438 [inline]
 kvm_free_vcpus arch/x86/kvm/x86.c:8888 [inline]
 kvm_arch_destroy_vm+0x365/0x7c0 arch/x86/kvm/x86.c:8985
 kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:751 [inline]
 kvm_put_kvm+0x6c8/0xff0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:772
 kvm_vcpu_release+0x7b/0xa0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2406
 __fput+0x3bc/0xa70 fs/file_table.c:279
 ____fput+0x15/0x20 fs/file_table.c:312
 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
 get_signal+0x1556/0x1970 kernel/signal.c:2347
 do_signal+0x9c/0x21e0 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop+0x2e5/0x380 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457679
Code: 1d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 eb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fea08457c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: fffffffffffffffc RBX: 00007fea084586d4 RCX: 0000000000457679
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000006
RBP: 000000000072bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004d0078 R14: 00000000004c016d R15: 0000000000000001

Allocated by task 8194:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
 kmem_cache_alloc+0x12e/0x730 mm/slab.c:3554
 kmem_cache_zalloc include/linux/slab.h:731 [inline]
 vmx_create_vcpu+0xcf/0x25c0 arch/x86/kvm/vmx.c:10954
 kvm_arch_vcpu_create+0xe5/0x220 arch/x86/kvm/x86.c:8452
 kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:2475 [inline]
 kvm_vm_ioctl+0x472/0x1d60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2976
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
 __do_sys_ioctl fs/ioctl.c:709 [inline]
 __se_sys_ioctl fs/ioctl.c:707 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8196:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kmem_cache_free+0x83/0x290 mm/slab.c:3756
 vmx_free_vcpu+0x26b/0x300 arch/x86/kvm/vmx.c:10948
 kvm_arch_vcpu_free arch/x86/kvm/x86.c:8438 [inline]
 kvm_free_vcpus arch/x86/kvm/x86.c:8888 [inline]
 kvm_arch_destroy_vm+0x365/0x7c0 arch/x86/kvm/x86.c:8985
 kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:751 [inline]
 kvm_put_kvm+0x6c8/0xff0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:772
 kvm_vcpu_release+0x7b/0xa0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2406
 __fput+0x3bc/0xa70 fs/file_table.c:279
 ____fput+0x15/0x20 fs/file_table.c:312
 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
 get_signal+0x1556/0x1970 kernel/signal.c:2347
 do_signal+0x9c/0x21e0 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop+0x2e5/0x380 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801ce1d8ac0
 which belongs to the cache kvm_vcpu(97:syz5) of size 23872
The buggy address is located 16 bytes inside of
 23872-byte region [ffff8801ce1d8ac0, ffff8801ce1de800)
The buggy address belongs to the page:
page:ffffea0007387600 count:1 mapcount:0 mapping:ffff8801c8c7f1c0 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000010200(slab|head)
raw: 02fffc0000010200 ffffea0007013408 ffffea00073a8a08 ffff8801c8c7f1c0
raw: 0000000000000000 ffff8801ce1d8ac0 0000000100000001 ffff880194aba140
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff880194aba140

Memory state around the buggy address:
 ffff8801ce1d8980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801ce1d8a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801ce1d8a80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                 ^
 ffff8801ce1d8b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ce1d8b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================