Hello,

syzbot hit the following crash on upstream commit
8dd903d2cf7b6dfe98be7c19f891882583c7266e (Fri Jan 19 23:20:00 2018 +0000)
Merge tag 'scsi-fixes' of  
git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

So far this crash happened 211 times on linux-next, mmots, upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

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Reported-by: syzbot+779c85f1b6798c06885b@syzkaller.appspotmail.com
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details.
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==================================================================
BUG: KASAN: use-after-free in __wake_up_common+0x670/0x780  
kernel/sched/wait.c:90
Read of size 8 at addr ffff8801bcf80f08 by task syzkaller194205/3724

CPU: 0 PID: 3724 Comm: syzkaller194205 Not tainted 4.15.0-rc8+ #270
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
  __wake_up_common+0x670/0x780 kernel/sched/wait.c:90
  __wake_up_common_lock+0x1b4/0x310 kernel/sched/wait.c:125
  __wake_up+0xe/0x10 kernel/sched/wait.c:149
  eventfd_release+0x4a/0x60 fs/eventfd.c:112
  __fput+0x327/0x7e0 fs/file_table.c:210
  ____fput+0x15/0x20 fs/file_table.c:244
  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:865
  do_group_exit+0x149/0x400 kernel/exit.c:968
  get_signal+0x73f/0x16c0 kernel/signal.c:2335
  do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809
  exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
  prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
  syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
  entry_SYSCALL_64_fastpath+0x9e/0xa0
RIP: 0033:0x449ac9
RSP: 002b:00007f0696bfbda8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: 0000000000000000 RBX: 00000000006dbc24 RCX: 0000000000449ac9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000006dbc24
RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 6f68762f7665642f
R13: 006563696d2f7475 R14: 706e692f7665642f R15: 0000000000000008

Allocated by task 3724:
  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
  __do_kmalloc_node mm/slab.c:3672 [inline]
  __kmalloc_node+0x47/0x70 mm/slab.c:3679
  kmalloc_node include/linux/slab.h:541 [inline]
  kvmalloc_node+0x64/0xd0 mm/util.c:397
  kvmalloc include/linux/mm.h:541 [inline]
  vhost_net_open+0x27/0x670 drivers/vhost/net.c:902
  misc_open+0x382/0x500 drivers/char/misc.c:154
  chrdev_open+0x257/0x730 fs/char_dev.c:417
  do_dentry_open+0x667/0xd40 fs/open.c:752
  vfs_open+0x107/0x220 fs/open.c:866
  do_last fs/namei.c:3379 [inline]
  path_openat+0x1151/0x3530 fs/namei.c:3519
  do_filp_open+0x25b/0x3b0 fs/namei.c:3554
  do_sys_open+0x502/0x6d0 fs/open.c:1059
  SYSC_openat fs/open.c:1086 [inline]
  SyS_openat+0x30/0x40 fs/open.c:1080
  entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 3724:
  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:3488 [inline]
  kfree+0xd6/0x260 mm/slab.c:3803
  kvfree+0x36/0x60 mm/util.c:416
  vhost_net_release+0x159/0x190 drivers/vhost/net.c:1012
  __fput+0x327/0x7e0 fs/file_table.c:210
  ____fput+0x15/0x20 fs/file_table.c:244
  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:865
  do_group_exit+0x149/0x400 kernel/exit.c:968
  get_signal+0x73f/0x16c0 kernel/signal.c:2335
  do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809
  exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
  prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
  syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
  entry_SYSCALL_64_fastpath+0x9e/0xa0

The buggy address belongs to the object at ffff8801bcf80c80
  which belongs to the cache kmalloc-65536 of size 65536
The buggy address is located 648 bytes inside of
  65536-byte region [ffff8801bcf80c80, ffff8801bcf90c80)
The buggy address belongs to the page:
page:ffffea0006f3e000 count:1 mapcount:0 mapping:ffff8801bcf80c80 index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801bcf80c80 0000000000000000 0000000100000001
raw: ffffea0006f26820 ffffea0006f3e820 ffff8801dac02500 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801bcf80e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801bcf80e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801bcf80f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                       ^
  ffff8801bcf80f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801bcf81000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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