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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 ffff8801a4731420 by task syzkaller271366/5171

CPU: 1 PID: 5171 Comm: syzkaller271366 Not tainted 4.15.0+ #288
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
 SYSC_exit_group kernel/exit.c:979 [inline]
 SyS_exit_group+0x1d/0x20 kernel/exit.c:977
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x4462c9
RSP: 002b:00007ffedaec08e8 EFLAGS: 00000206 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007f6576f23700 RCX: 00000000004462c9
RDX: 00000000004462c9 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 00007ffedaec0890 R08: 0000000000000000 R09: 0000000000000003
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007ffedaec07ef R14: 00007f6576f239c0 R15: 0000000000000007

Allocated by task 5172:
 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:3397 [inline]
 path_openat+0x1151/0x3530 fs/namei.c:3537
 do_filp_open+0x25b/0x3b0 fs/namei.c:3572
 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 5171:
 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
 SYSC_exit_group kernel/exit.c:979 [inline]
 SyS_exit_group+0x1d/0x20 kernel/exit.c:977
 entry_SYSCALL_64_fastpath+0x29/0xa0

The buggy address belongs to the object at ffff8801a472cb40
 which belongs to the cache kmalloc-65536 of size 65536
The buggy address is located 18656 bytes inside of
 65536-byte region [ffff8801a472cb40, ffff8801a473cb40)
The buggy address belongs to the page:
page:ffffea000691c800 count:1 mapcount:0 mapping:ffff8801a472cb40 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801a472cb40 0000000000000000 0000000100000001
raw: ffffea000691c020 ffffea000691d020 ffff8801db002500 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801a4731300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801a4731380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801a4731400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff8801a4731480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801a4731500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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