BUG: KASAN: use-after-free in __write_once_size include/linux/compiler.h:305 [inline]
BUG: KASAN: use-after-free in __hlist_del include/linux/list.h:648 [inline]
BUG: KASAN: use-after-free in detach_timer kernel/time/timer.c:791 [inline]
BUG: KASAN: use-after-free in detach_if_pending+0x557/0x610 kernel/time/timer.c:808
Write of size 8 at addr ffff8801cf04b7c0 by task syzkaller826880/2986

CPU: 1 PID: 2986 Comm: syzkaller826880 Not tainted 4.13.0-rc7-next-20170901+ #13
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x24e/0x340 mm/kasan/report.c:409
 __asan_report_store8_noabort+0x17/0x20 mm/kasan/report.c:435
 __write_once_size include/linux/compiler.h:305 [inline]
 __hlist_del include/linux/list.h:648 [inline]
 detach_timer kernel/time/timer.c:791 [inline]
 detach_if_pending+0x557/0x610 kernel/time/timer.c:808
 try_to_del_timer_sync+0xa2/0x120 kernel/time/timer.c:1182
 del_timer_sync+0x18a/0x240 kernel/time/timer.c:1247
 tun_flow_uninit drivers/net/tun.c:1104 [inline]
 tun_free_netdev+0x105/0x1b0 drivers/net/tun.c:1762
 netdev_run_todo+0x870/0xca0 net/core/dev.c:7856
 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:106
 tun_detach drivers/net/tun.c:588 [inline]
 tun_chr_close+0x49/0x60 drivers/net/tun.c:2595
 __fput+0x333/0x7f0 fs/file_table.c:210
 ____fput+0x15/0x20 fs/file_table.c:246
 task_work_run+0x199/0x270 kernel/task_work.c:112
 exit_task_work include/linux/task_work.h:21 [inline]
 do_exit+0xa52/0x1b40 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+0x1f/0xbe
RIP: 0033:0x444db9
RSP: 002b:00007ffd7ae7b7f8 EFLAGS: 00000206 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007ffd7ae7b840 RCX: 0000000000444db9
RDX: 0000000000444db9 RSI: 00000000207dcfd8 RDI: 0000000000000001
RBP: 0000000000000082 R08: 0000000000000000 R09: 00007ffd7ae7b840
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000402160
R13: 00000000004021f0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 2986:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 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:3689 [inline]
 __kmalloc_node+0x47/0x70 mm/slab.c:3696
 kmalloc_node include/linux/slab.h:535 [inline]
 kvmalloc_node+0x64/0xd0 mm/util.c:397
 kvmalloc include/linux/mm.h:529 [inline]
 kvzalloc include/linux/mm.h:537 [inline]
 alloc_netdev_mqs+0x16e/0xed0 net/core/dev.c:8010
 tun_set_iff drivers/net/tun.c:2008 [inline]
 __tun_chr_ioctl+0x12be/0x3d20 drivers/net/tun.c:2262
 tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2507
 vfs_ioctl fs/ioctl.c:45 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 2986:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 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:3503 [inline]
 kfree+0xca/0x250 mm/slab.c:3820
 kvfree+0x36/0x60 mm/util.c:416
 netdev_freemem net/core/dev.c:7962 [inline]
 free_netdev+0x2cf/0x360 net/core/dev.c:8124
 tun_set_iff drivers/net/tun.c:2091 [inline]
 __tun_chr_ioctl+0x2cf6/0x3d20 drivers/net/tun.c:2262
 tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2507
 vfs_ioctl fs/ioctl.c:45 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x1f/0xbe

The buggy address belongs to the object at ffff8801cf0483c0
 which belongs to the cache kmalloc-16384 of size 16384
The buggy address is located 13312 bytes inside of
 16384-byte region [ffff8801cf0483c0, ffff8801cf04c3c0)
The buggy address belongs to the page:
page:ffffea00073c1200 count:1 mapcount:0 mapping:ffff8801cf0483c0 index:0x0 compound_mapcount: 0
flags: 0x200000000008100(slab|head)
raw: 0200000000008100 ffff8801cf0483c0 0000000000000000 0000000100000001
raw: ffffea000738f220 ffff8801dac01c50 ffff8801dac02200 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cf04b680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801cf04b700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801cf04b780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff8801cf04b800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801cf04b880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================