Date:   Wed, 20 Dec 2017 08:03:02 -0800
From:   syzbot 
        <bot+1ab0ab6049e3e38c56d313bd2982bbf6b007ad6c@...kaller.appspotmail.com>
To:     hpa@...or.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, pbonzini@...hat.com, rkrcmar@...hat.com,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de, x86@...nel.org
Subject: KASAN: use-after-free Read in __schedule

Hello,

syzkaller hit the following crash on  
7dc9f647127d6955ffacaf51cb6a627b31dceec2
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


kvm: KVM_SET_TSS_ADDR need to be called before entering vcpu
==================================================================
BUG: KASAN: use-after-free in __fire_sched_out_preempt_notifiers  
kernel/sched/core.c:2550 [inline]
BUG: KASAN: use-after-free in fire_sched_out_preempt_notifiers  
kernel/sched/core.c:2558 [inline]
BUG: KASAN: use-after-free in prepare_task_switch kernel/sched/core.c:2594  
[inline]
BUG: KASAN: use-after-free in context_switch kernel/sched/core.c:2765  
[inline]
BUG: KASAN: use-after-free in __schedule+0xda3/0x2060  
kernel/sched/core.c:3376
Read of size 8 at addr ffff8801c8cb8058 by task syzkaller738410/3153

CPU: 1 PID: 3153 Comm: syzkaller738410 Not tainted  
4.15.0-rc4-next-20171220+ #77
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
  print_address_description+0x73/0x250 mm/kasan/report.c:252
  kasan_report_error mm/kasan/report.c:351 [inline]
  kasan_report+0x25b/0x340 mm/kasan/report.c:409
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
  __fire_sched_out_preempt_notifiers kernel/sched/core.c:2550 [inline]
  fire_sched_out_preempt_notifiers kernel/sched/core.c:2558 [inline]
  prepare_task_switch kernel/sched/core.c:2594 [inline]
  context_switch kernel/sched/core.c:2765 [inline]
  __schedule+0xda3/0x2060 kernel/sched/core.c:3376
  preempt_schedule_common+0x22/0x60 kernel/sched/core.c:3515
  _cond_resched+0x1d/0x30 kernel/sched/core.c:4852
  __wait_for_common kernel/sched/completion.c:107 [inline]
  wait_for_common kernel/sched/completion.c:123 [inline]
  wait_for_completion+0xa5/0x770 kernel/sched/completion.c:144
  __synchronize_srcu+0x1ad/0x260 kernel/rcu/srcutree.c:925
  synchronize_srcu_expedited kernel/rcu/srcutree.c:950 [inline]
  synchronize_srcu+0x1a3/0x570 kernel/rcu/srcutree.c:1001
  kvm_page_track_unregister_notifier+0x186/0x270  
arch/x86/kvm/page_track.c:213
  kvm_mmu_uninit_vm+0x1c/0x20 arch/x86/kvm/mmu.c:5053
  kvm_arch_destroy_vm+0x73b/0x980 arch/x86/kvm/x86.c:8418
  kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:728 [inline]
  kvm_put_kvm+0x695/0xde0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:749
  kvm_vm_release+0x42/0x50 arch/x86/kvm/../../../virt/kvm/kvm_main.c:760
  __fput+0x327/0x7e0 fs/file_table.c:209
  ____fput+0x15/0x20 fs/file_table.c:243
  task_work_run+0x199/0x270 kernel/task_work.c:113
  exit_task_work include/linux/task_work.h:22 [inline]
  do_exit+0x9bb/0x1ad0 kernel/exit.c:869
  do_group_exit+0x149/0x400 kernel/exit.c:972
  SYSC_exit_group kernel/exit.c:983 [inline]
  SyS_exit_group+0x1d/0x20 kernel/exit.c:981
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x43ee18
RSP: 002b:00007ffcbff2d938 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 000000000043ee18
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000006ca018 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401b40
R13: 0000000000401bd0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3153:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
  kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
  kmem_cache_alloc+0x12e/0x760 mm/slab.c:3545
  kmem_cache_zalloc include/linux/slab.h:695 [inline]
  vmx_create_vcpu+0xc4/0x2f20 arch/x86/kvm/vmx.c:9819
  kvm_arch_vcpu_create+0x12c/0x1a0 arch/x86/kvm/x86.c:7884
  kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:2445  
[inline]
  kvm_vm_ioctl+0x48b/0x1c60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2943
  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+0x1f/0x96

Freed by task 3153:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
  __cache_free mm/slab.c:3489 [inline]
  kmem_cache_free+0x83/0x2a0 mm/slab.c:3747
  vmx_free_vcpu+0x1ee/0x260 arch/x86/kvm/vmx.c:9813
  kvm_arch_vcpu_free arch/x86/kvm/x86.c:7870 [inline]
  kvm_free_vcpus arch/x86/kvm/x86.c:8317 [inline]
  kvm_arch_destroy_vm+0x4a2/0x980 arch/x86/kvm/x86.c:8416
  kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:728 [inline]
  kvm_put_kvm+0x695/0xde0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:749
  kvm_vm_release+0x42/0x50 arch/x86/kvm/../../../virt/kvm/kvm_main.c:760
  __fput+0x327/0x7e0 fs/file_table.c:209
  ____fput+0x15/0x20 fs/file_table.c:243
  task_work_run+0x199/0x270 kernel/task_work.c:113
  exit_task_work include/linux/task_work.h:22 [inline]
  do_exit+0x9bb/0x1ad0 kernel/exit.c:869
  do_group_exit+0x149/0x400 kernel/exit.c:972
  SYSC_exit_group kernel/exit.c:983 [inline]
  SyS_exit_group+0x1d/0x20 kernel/exit.c:981
  entry_SYSCALL_64_fastpath+0x1f/0x96

The buggy address belongs to the object at ffff8801c8cb8040
  which belongs to the cache kvm_vcpu of size 23872
The buggy address is located 24 bytes inside of
  23872-byte region [ffff8801c8cb8040, ffff8801c8cbdd80)
The buggy address belongs to the page:
page:00000000cd7a3442 count:1 mapcount:0 mapping:00000000f1888586 index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801c8cb8040 0000000000000000 0000000100000001
raw: ffff8801d6426748 ffff8801d6426748 ffff8801d6430c00 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801c8cb7f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801c8cb7f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801c8cb8000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                     ^
  ffff8801c8cb8080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801c8cb8100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
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