==================================================================
BUG: KASAN: use-after-free in __write_once_size include/linux/compiler.h:247 [inline]
BUG: KASAN: use-after-free in __hlist_del include/linux/list.h:632 [inline]
BUG: KASAN: use-after-free in hlist_del_rcu include/linux/rculist.h:340 [inline]
BUG: KASAN: use-after-free in nf_nat_cleanup_conntrack+0x1ca/0x1e0 net/netfilter/nf_nat_core.c:691
Write of size 8 at addr ffff8800a7770d40 by task syz-executor.0/3668

CPU: 0 PID: 3668 Comm: syz-executor.0 Not tainted 4.4.174+ #17
 0000000000000000[   92.234760] SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket
 71ab418799d26d2f ffff8801db607a10 ffffffff81aad1a1
 0000000000000001 ffffea00029ddc00 ffff8800a7770d40 0000000000000008
 ffffffff82361100 ffff8801db607a48 ffffffff81490120 0000000000000001
Call Trace:
 <IRQ>  [<ffffffff81aad1a1>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ>  [<ffffffff81aad1a1>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff81490120>] print_address_description+0x6f/0x21b mm/kasan/report.c:252
 [<ffffffff81490358>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff81490358>] kasan_report mm/kasan/report.c:408 [inline]
 [<ffffffff81490358>] kasan_report.cold+0x8c/0x2be mm/kasan/report.c:393
 [<ffffffff81484f77>] __asan_report_store8_noabort+0x17/0x20 mm/kasan/report.c:434
 [<ffffffff823612ca>] __write_once_size include/linux/compiler.h:247 [inline]
 [<ffffffff823612ca>] __hlist_del include/linux/list.h:632 [inline]
 [<ffffffff823612ca>] hlist_del_rcu include/linux/rculist.h:340 [inline]
 [<ffffffff823612ca>] nf_nat_cleanup_conntrack+0x1ca/0x1e0 net/netfilter/nf_nat_core.c:691
 [<ffffffff8232d7b0>] __nf_ct_ext_destroy+0x140/0x2a0 net/netfilter/nf_conntrack_extend.c:40
 [<ffffffff8230e217>] nf_ct_ext_destroy include/net/netfilter/nf_conntrack_extend.h:80 [inline]
 [<ffffffff8230e217>] nf_conntrack_free+0x77/0x120 net/netfilter/nf_conntrack_core.c:904
 [<ffffffff823116f0>] destroy_conntrack+0x270/0x380 net/netfilter/nf_conntrack_core.c:365
 [<ffffffff822f6cd9>] nf_conntrack_destroy+0x99/0x1a0 net/netfilter/core.c:389
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket
 [<ffffffff821eff3a>] nf_conntrack_put include/linux/skbuff.h:3377 [inline]
 [<ffffffff821eff3a>] skb_release_head_state+0x15a/0x210 net/core/skbuff.c:649
 [<ffffffff821fd0e6>] skb_release_all+0x16/0x60 net/core/skbuff.c:659
 [<ffffffff821fd257>] __kfree_skb net/core/skbuff.c:675 [inline]
 [<ffffffff821fd257>] kfree_skb+0xf7/0x400 net/core/skbuff.c:696
 [<ffffffff823b8e9a>] inet_frag_rbtree_purge+0xaa/0xf0 net/ipv4/ip_fragment.c:761
 [<ffffffff824e152f>] inet_frag_destroy+0x21f/0x2c0 net/ipv4/inet_fragment.c:156
 [<ffffffff823b8f14>] inet_frag_put include/net/inet_frag.h:124 [inline]
 [<ffffffff823b8f14>] ipq_put+0x34/0x40 net/ipv4/ip_fragment.c:164
 [<ffffffff823b954d>] ip_expire+0x14d/0x880 net/ipv4/ip_fragment.c:265
 [<ffffffff812582dd>] call_timer_fn+0x18d/0x850 kernel/time/timer.c:1185
 [<ffffffff81258ebf>] __run_timers kernel/time/timer.c:1261 [inline]
 [<ffffffff81258ebf>] run_timer_softirq+0x51f/0xb70 kernel/time/timer.c:1444
 [<ffffffff8271bb16>] __do_softirq+0x226/0xa3f kernel/softirq.c:273
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=65535 sclass=netlink_route_socket
 [<ffffffff810e1a8a>] invoke_softirq kernel/softirq.c:350 [inline]
 [<ffffffff810e1a8a>] irq_exit+0x10a/0x150 kernel/softirq.c:391
 [<ffffffff8271b24e>] exiting_irq arch/x86/include/asm/apic.h:652 [inline]
 [<ffffffff8271b24e>] smp_apic_timer_interrupt+0x7e/0xb0 arch/x86/kernel/apic/apic.c:926
 [<ffffffff8271a59d>] apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:768
 <EOI>  [<ffffffff811fb28b>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:812 [inline]
 <EOI>  [<ffffffff811fb28b>] ? lock_is_held+0xfb/0x140 kernel/locking/lockdep.c:3632
 [<ffffffff81159bea>] ___might_sleep+0x1ca/0x280 kernel/sched/core.c:7956
 [<ffffffff81159d30>] __might_sleep+0x90/0x1a0 kernel/sched/core.c:7948
 [<ffffffff8145554a>] anon_vma_prepare+0x5a/0x3d0 mm/rmap.c:174
 [<ffffffff8142fbf6>] wp_page_copy.isra.0+0xb6/0xc70 mm/memory.c:2159
 [<ffffffff81433bda>] do_wp_page+0x23a/0x1340 mm/memory.c:2441
 [<ffffffff8143b2e4>] handle_pte_fault mm/memory.c:3362 [inline]
 [<ffffffff8143b2e4>] __handle_mm_fault mm/memory.c:3474 [inline]
 [<ffffffff8143b2e4>] handle_mm_fault+0x1614/0x3140 mm/memory.c:3503
 [<ffffffff810aaa4e>] __do_page_fault+0x28e/0x7f0 arch/x86/mm/fault.c:1243
 [<ffffffff810ab008>] do_page_fault+0x28/0x30 arch/x86/mm/fault.c:1306
 [<ffffffff82719e35>] page_fault+0x25/0x30 arch/x86/entry/entry_64.S:1064
 [<ffffffff814b17a4>] pipe_read+0x274/0x860 fs/pipe.c:270
 [<ffffffff81496725>] new_sync_read fs/read_write.c:424 [inline]
 [<ffffffff81496725>] __vfs_read+0x2e5/0x3c0 fs/read_write.c:436
 [<ffffffff81498264>] vfs_read+0x134/0x360 fs/read_write.c:456
 [<ffffffff8149aa8c>] SYSC_read fs/read_write.c:571 [inline]
 [<ffffffff8149aa8c>] SyS_read+0xdc/0x1c0 fs/read_write.c:564
 [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

The buggy address belongs to the page:
page:ffffea00029ddc00 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x0()
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8800a7770c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8800a7770c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8800a7770d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff8800a7770d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8800a7770e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================