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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 ffff8800a6541788 by task syz-executor.3/12194

CPU: 1 PID: 12194 Comm: syz-executor.3 Not tainted 4.4.174+ #17
 0000000000000000 d09121717b4bf1e0 ffff8801db707a10 ffffffff81aad1a1
 0000000000000001 ffffea0002995040 ffff8800a6541788 0000000000000008
 ffffffff82361100 ffff8801db707a48 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
 [<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
 [<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>  [<ffffffff8271802f>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:812 [inline]
 <EOI>  [<ffffffff8271802f>] ? __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:162 [inline]
 <EOI>  [<ffffffff8271802f>] ? _raw_spin_unlock_irqrestore+0x5f/0x70 kernel/locking/spinlock.c:191
 [<ffffffff81b0d33d>] debug_object_active_state+0x25d/0x380 lib/debugobjects.c:665
 [<ffffffff812446de>] debug_rcu_head_queue kernel/rcu/rcu.h:76 [inline]
 [<ffffffff812446de>] __call_rcu.constprop.0+0x4e/0x930 kernel/rcu/tree.c:3059
 [<ffffffff81244fd2>] call_rcu+0x12/0x20 kernel/rcu/tree_plugin.h:662
 [<ffffffff822575c1>] dst_release+0xa1/0xb0 net/core/dst.c:311
 [<ffffffff823b1876>] ipv4_blackhole_route+0x5e6/0x720 net/ipv4/route.c:2423
 [<ffffffff825523f4>] make_blackhole net/xfrm/xfrm_policy.c:2161 [inline]
 [<ffffffff825523f4>] xfrm_lookup_route net/xfrm/xfrm_policy.c:2331 [inline]
 [<ffffffff825523f4>] xfrm_lookup_route+0xf4/0x140 net/xfrm/xfrm_policy.c:2322
 [<ffffffff823a5a23>] ip_route_output_flow+0x93/0xa0 net/ipv4/route.c:2437
 [<ffffffff8247fa07>] udp_sendmsg+0x1537/0x1c60 net/ipv4/udp.c:1040
 [<ffffffff826137a2>] udpv6_sendmsg+0x12f2/0x24f0 net/ipv6/udp.c:1173
 [<ffffffff824a8b42>] inet_sendmsg+0x202/0x4d0 net/ipv4/af_inet.c:755
 [<ffffffff821d838e>] sock_sendmsg_nosec net/socket.c:638 [inline]
 [<ffffffff821d838e>] sock_sendmsg+0xbe/0x110 net/socket.c:648
 [<ffffffff821d9e69>] ___sys_sendmsg+0x369/0x890 net/socket.c:1975
 [<ffffffff821dd386>] __sys_sendmmsg+0x1d6/0x2e0 net/socket.c:2053
 [<ffffffff822ace22>] C_SYSC_sendmmsg net/compat.c:731 [inline]
 [<ffffffff822ace22>] compat_SyS_sendmmsg+0x32/0x40 net/compat.c:728
 [<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:ffffea0002995040 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x0()
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8800a6541680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8800a6541700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8800a6541780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff8800a6541800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8800a6541880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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