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:519 [inline]
BUG: KASAN: use-after-free in __internal_add_timer+0x275/0x2d0 kernel/time/timer.c:530
Write of size 8 at addr ffff8801d4c6b6c8 by task syzkaller191108/3039

CPU: 1 PID: 3039 Comm: syzkaller191108 Not tainted 4.13.0-rc6-next-20170823+ #7
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
 hlist_add_head include/linux/list.h:673 [inline]
 enqueue_timer kernel/time/timer.c:519 [inline]
 __internal_add_timer+0x275/0x2d0 kernel/time/timer.c:530
 internal_add_timer kernel/time/timer.c:572 [inline]
 __mod_timer kernel/time/timer.c:1012 [inline]
 mod_timer+0x6e8/0xf40 kernel/time/timer.c:1059
 tun_flow_init drivers/net/tun.c:1098 [inline]
 tun_set_iff drivers/net/tun.c:2044 [inline]
 __tun_chr_ioctl+0x1b2c/0x3d40 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
RIP: 0033:0x443e09
RSP: 002b:00007ffde43e2a78 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000443e09
RDX: 0000000020982fd8 RSI: 00000000400454ca RDI: 0000000000000004
RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 8a43cf6a0d164a66
R13: 74656e2f7665642f R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3039:
 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:8009
 tun_set_iff drivers/net/tun.c:2008 [inline]
 __tun_chr_ioctl+0x12be/0x3d40 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 3039:
 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:7961 [inline]
 free_netdev+0x2cf/0x360 net/core/dev.c:8123
 tun_set_iff drivers/net/tun.c:2091 [inline]
 __tun_chr_ioctl+0x2cff/0x3d40 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 ffff8801d4c682c0
 which belongs to the cache kmalloc-16384 of size 16384
The buggy address is located 13320 bytes inside of
 16384-byte region [ffff8801d4c682c0, ffff8801d4c6c2c0)
The buggy address belongs to the page:
page:ffffea0007531a00 count:1 mapcount:0 mapping:ffff8801d4c682c0 index:0x0 compound_mapcount: 0
flags: 0x200000000008100(slab|head)
raw: 0200000000008100 ffff8801d4c682c0 0000000000000000 0000000100000001
raw: ffffea0007485c20 ffffea0006fe4a20 ffff8801dac02200 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d4c6b580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d4c6b600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d4c6b680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff8801d4c6b700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d4c6b780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================