BUG: KASAN: use-after-free in hlist_add_head include/linux/list.h:673 [inline]
BUG: KASAN: use-after-free in enqueue_timer kernel/time/timer.c:520 [inline]
BUG: KASAN: use-after-free in __internal_add_timer+0x275/0x2d0 kernel/time/timer.c:531
Write of size 8 at addr ffff8801ce52b688 by task syzkaller367658/2983

CPU: 1 PID: 2983 Comm: syzkaller367658 Not tainted 4.14.0-rc4-mm1+ #16
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+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_store8_noabort+0x17/0x20 mm/kasan/report.c:435
 hlist_add_head include/linux/list.h:673 [inline]
 enqueue_timer kernel/time/timer.c:520 [inline]
 __internal_add_timer+0x275/0x2d0 kernel/time/timer.c:531
 internal_add_timer kernel/time/timer.c:573 [inline]
 __mod_timer kernel/time/timer.c:1024 [inline]
 mod_timer+0x622/0x15b0 kernel/time/timer.c:1071
 tun_flow_init drivers/net/tun.c:1194 [inline]
 tun_set_iff drivers/net/tun.c:2281 [inline]
 __tun_chr_ioctl+0x1beb/0x3e40 drivers/net/tun.c:2499
 tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2744
 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
RIP: 0033:0x443d79
RSP: 002b:00007fff93348218 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0f1c35cd67fe3811 RCX: 0000000000443d79
RDX: 0000000020fd4fd8 RSI: 00000000400454ca RDI: 0000000000000004
RBP: 0000000000000082 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: c23c83788a2ba035
R13: 74656e2f7665642f R14: 0000000000000000 R15: 0000000000000000

Allocated by task 2983:
 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:3676 [inline]
 __kmalloc_node+0x47/0x70 mm/slab.c:3683
 kmalloc_node include/linux/slab.h:544 [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+0x16d/0xed0 net/core/dev.c:8091
 tun_set_iff drivers/net/tun.c:2245 [inline]
 __tun_chr_ioctl+0x1386/0x3e40 drivers/net/tun.c:2499
 tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2744
 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 2983:
 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:3492 [inline]
 kfree+0xca/0x250 mm/slab.c:3807
 kvfree+0x36/0x60 mm/util.c:416
 netdev_freemem net/core/dev.c:8043 [inline]
 free_netdev+0x2cf/0x360 net/core/dev.c:8205
 tun_set_iff drivers/net/tun.c:2328 [inline]
 __tun_chr_ioctl+0x2df6/0x3e40 drivers/net/tun.c:2499
 tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2744
 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 ffff8801ce528280
 which belongs to the cache kmalloc-16384 of size 16384
The buggy address is located 13320 bytes inside of
 16384-byte region [ffff8801ce528280, ffff8801ce52c280)
The buggy address belongs to the page:
page:ffffea0007394a00 count:1 mapcount:0 mapping:ffff8801ce528280 index:0x0 compound_mapcount: 0
flags: 0x200000000008100(slab|head)
raw: 0200000000008100 ffff8801ce528280 0000000000000000 0000000100000001
raw: ffffea000701a820 ffffea00073a5e20 ffff8801dac02200 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801ce52b580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ce52b600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801ce52b680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff8801ce52b700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ce52b780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================