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


kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 4227 Comm: syzkaller244813 Not tainted  
4.15.0-rc4-next-20171220+ #77
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__fire_sched_in_preempt_notifiers kernel/sched/core.c:2534  
[inline]
RIP: 0010:fire_sched_in_preempt_notifiers kernel/sched/core.c:2540 [inline]
RIP: 0010:finish_task_switch+0x42d/0x740 kernel/sched/core.c:2670
RSP: 0018:ffff8801c284f3b8 EFLAGS: 00010a06
RAX: dffffc0000000000 RBX: ffff8801db22c900 RCX: 1bd5a00000000022
RDX: 0000000000000000 RSI: 1ffff10038509e20 RDI: dead000000000110
RBP: ffff8801c284f468 R08: 1ffff10038661af3 R09: 0000000000000000
R10: ffff8801c284f390 R11: 0000000000000000 R12: ffff8801c2eca100
R13: 1ffff10038509e7c R14: dffffc0000000000 R15: dead000000000100
FS:  00007f7f034c8700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7ee8491e78 CR3: 00000001ca6c9003 CR4: 00000000001626f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  context_switch kernel/sched/core.c:2803 [inline]
  __schedule+0x8f3/0x2060 kernel/sched/core.c:3376
  preempt_schedule_common+0x22/0x60 kernel/sched/core.c:3515
  _cond_resched+0x1d/0x30 kernel/sched/core.c:4852
  zap_pmd_range mm/memory.c:1443 [inline]
  zap_pud_range mm/memory.c:1470 [inline]
  zap_p4d_range mm/memory.c:1491 [inline]
  unmap_page_range+0x872/0x22e0 mm/memory.c:1512
  unmap_single_vma+0x15f/0x2d0 mm/memory.c:1557
  zap_page_range+0x35c/0x5f0 mm/memory.c:1611
  madvise_dontneed_single_vma mm/madvise.c:510 [inline]
  madvise_dontneed_free mm/madvise.c:563 [inline]
  madvise_vma mm/madvise.c:688 [inline]
  SYSC_madvise mm/madvise.c:863 [inline]
  SyS_madvise+0xf9e/0x13d0 mm/madvise.c:791
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x448fe7
RSP: 002b:00007f7f034c7dd8 EFLAGS: 00000206 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007f7f034c6970 RCX: 0000000000448fe7
RDX: 0000000000000004 RSI: 00000000007fb000 RDI: 00007f7f02cc8000
RBP: 000000000000003f R08: 0000000000000012 R09: 0000000000000000
R10: 00008c0000500000 R11: 0000000000000206 R12: 0000000000000000
R13: 00000000ffffffff R14: ffffffffffffffff R15: 00000000206a2000
Code: ff 11 4c 89 f9 48 c1 e9 03 42 80 3c 31 00 0f 85 1b 02 00 00 4d 8b 3f  
4d 85 ff 0f 84 c0 fd ff ff 49 8d 7f 10 48 89 f9 48 c1 e9 03 <42> 80 3c 31  
00 74 ae e8 a7 cc 5b 00 eb a7 4c 89 fe 4c 89 e7 e8
RIP: __fire_sched_in_preempt_notifiers kernel/sched/core.c:2534 [inline]  
RSP: ffff8801c284f3b8
RIP: fire_sched_in_preempt_notifiers kernel/sched/core.c:2540 [inline] RSP:  
ffff8801c284f3b8
RIP: finish_task_switch+0x42d/0x740 kernel/sched/core.c:2670 RSP:  
ffff8801c284f3b8
---[ end trace 4048fa81110fa823 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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