syzbot

ExceptionBitmap=00060042 PFECmask=00000000 PFECmatch=00000000
EPT pointer = 0x00000001bc3b001e
VMEntry: intr_info=80000000 errcode=00000000 ilen=00000000
==================================================================
VMExit: intr_info=00000000 errcode=00000000 ilen=00000002
BUG: KASAN: use-after-free in __write_once_size include/linux/compiler.h:215 [inline]
BUG: KASAN: use-after-free in __hlist_del include/linux/list.h:679 [inline]
BUG: KASAN: use-after-free in hlist_del include/linux/list.h:686 [inline]
BUG: KASAN: use-after-free in preempt_notifier_unregister+0x1da/0x250 kernel/sched/core.c:2472
Write of size 8 at addr ffff8801c7868990 by task syz-executor6/4705

CPU: 1 PID: 4705 Comm: syz-executor6 Not tainted 4.19.0-rc2+ #230
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+0x1c4/0x2b4 lib/dump_stack.c:113
 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
        reason=80000021 qualification=0000000000000000
 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
 __write_once_size include/linux/compiler.h:215 [inline]
 __hlist_del include/linux/list.h:679 [inline]
 hlist_del include/linux/list.h:686 [inline]
 preempt_notifier_unregister+0x1da/0x250 kernel/sched/core.c:2472
IDTVectoring: info=00000000 errcode=00000000
TSC Offset = 0xfffffe3896bf972d
 vcpu_put+0x28/0x60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:173
 kvm_arch_vcpu_ioctl_run+0xb01/0x16e0 arch/x86/kvm/x86.c:7897
 kvm_vcpu_ioctl+0x72b/0x1150 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2590
EPT pointer = 0x00000001c4c6401e
 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
RIP: 0033:0x457099
Code: fd 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 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f7b4bec3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f7b4bec46d4 RCX: 0000000000457099
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 0000000000930140 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004cf730 R14: 00000000004c59b9 R15: 0000000000000001

Allocated by task 4687:
 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_node+0x144/0x730 mm/slab.c:3644
 alloc_task_struct_node kernel/fork.c:157 [inline]
 dup_task_struct kernel/fork.c:802 [inline]
 copy_process+0x1ff4/0x8780 kernel/fork.c:1707
 _do_fork+0x1cb/0x11d0 kernel/fork.c:2166
 __do_sys_clone kernel/fork.c:2273 [inline]
 __se_sys_clone kernel/fork.c:2267 [inline]
 __x64_sys_clone+0xbf/0x150 kernel/fork.c:2267
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 5368:
 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
 free_task_struct kernel/fork.c:162 [inline]
 free_task+0x16e/0x1f0 kernel/fork.c:416
 __put_task_struct+0x2e6/0x620 kernel/fork.c:689
 put_task_struct include/linux/sched/task.h:96 [inline]
 delayed_put_task_struct+0x2ff/0x4c0 kernel/exit.c:181
 __rcu_reclaim kernel/rcu/rcu.h:236 [inline]
 rcu_do_batch kernel/rcu/tree.c:2576 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2880 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2847 [inline]
 rcu_process_callbacks+0xf23/0x2670 kernel/rcu/tree.c:2864
 __do_softirq+0x30b/0xad8 kernel/softirq.c:292

The buggy address belongs to the object at ffff8801c7868640
 which belongs to the cache task_struct(49:syz6) of size 6080
The buggy address is located 848 bytes inside of
 6080-byte region [ffff8801c7868640, ffff8801c7869e00)
The buggy address belongs to the page:
page:ffffea00071e1a00 count:1 mapcount:0 mapping:ffff8801d8a079c0 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffffea0006f7fb88 ffffea0007602d08 ffff8801d8a079c0
raw: 0000000000000000 ffff8801c7868640 0000000100000001 ffff8801c2da8a80
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff8801c2da8a80

Memory state around the buggy address:
 ffff8801c7868880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c7868900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801c7868980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8801c7868a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c7868a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================