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BUG: KASAN: use-after-free in ip6_dst_idev include/net/ip6_fib.h:141 [inline]
BUG: KASAN: use-after-free in ip6_xmit+0x1838/0x1b80 net/ipv6/ip6_output.c:254
Read of size 8 at addr ffff88018e46bb58 by task syz-executor0/3926

CPU: 1 PID: 3926 Comm: syz-executor0 Not tainted 4.9.124-g09eb2ba #83
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff88018282f540 ffffffff81eb95e9 ffffea0006391ac0 ffff88018e46bb58
 0000000000000000 ffff88018e46bb58 0000000000000040 ffff88018282f578
 ffffffff8156c35e ffff88018e46bb58 0000000000000008 0000000000000000
Call Trace:
 [<ffffffff81eb95e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb95e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8156c35e>] print_address_description+0x6c/0x234 mm/kasan/report.c:256
 [<ffffffff8156c768>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff8156c768>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
 [<ffffffff8153faf4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 [<ffffffff83562358>] ip6_dst_idev include/net/ip6_fib.h:141 [inline]
 [<ffffffff83562358>] ip6_xmit+0x1838/0x1b80 net/ipv6/ip6_output.c:254
 [<ffffffff836275ec>] inet6_csk_xmit+0x27c/0x4d0 net/ipv6/inet6_connection_sock.c:178
 [<ffffffff836c42e5>] l2tp_xmit_core net/l2tp/l2tp_core.c:1178 [inline]
 [<ffffffff836c42e5>] l2tp_xmit_skb+0xc45/0xf30 net/l2tp/l2tp_core.c:1273
 [<ffffffff836cf8b0>] pppol2tp_sendmsg+0x4e0/0x790 net/l2tp/l2tp_ppp.c:339
 [<ffffffff8301e0ac>] sock_sendmsg_nosec net/socket.c:648 [inline]
 [<ffffffff8301e0ac>] sock_sendmsg+0xcc/0x110 net/socket.c:658
 [<ffffffff8301f8ca>] ___sys_sendmsg+0x47a/0x840 net/socket.c:1982
 [<ffffffff83021e31>] __sys_sendmmsg+0x161/0x3d0 net/socket.c:2072
 [<ffffffff830220d5>] SYSC_sendmmsg net/socket.c:2103 [inline]
 [<ffffffff830220d5>] SyS_sendmmsg+0x35/0x60 net/socket.c:2098
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a019d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Allocated by task 3905:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:609
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:547
 slab_post_alloc_hook mm/slab.h:417 [inline]
 slab_alloc_node mm/slub.c:2715 [inline]
 slab_alloc mm/slub.c:2723 [inline]
 kmem_cache_alloc+0xbe/0x290 mm/slub.c:2728
 dst_alloc+0xb5/0x1a0 net/core/dst.c:210
 rt_dst_alloc+0x78/0x430 net/ipv4/route.c:1486
 ip_route_input_slow net/ipv4/route.c:1936 [inline]
 ip_route_input_noref+0x1aa7/0x38f0 net/ipv4/route.c:2038
 arp_process+0xd80/0x1e70 net/ipv4/arp.c:792
 NF_HOOK_THRESH include/linux/netfilter.h:232 [inline]
 NF_HOOK include/linux/netfilter.h:255 [inline]
 arp_rcv+0x4ec/0x780 net/ipv4/arp.c:943
 __netif_receive_skb_core+0x12a0/0x2a20 net/core/dev.c:4267
 __netif_receive_skb+0x5b/0x1c0 net/core/dev.c:4305
 process_backlog+0x206/0x6a0 net/core/dev.c:4926
 napi_poll net/core/dev.c:5227 [inline]
 net_rx_action+0x3c4/0xde0 net/core/dev.c:5292
 __do_softirq+0x210/0x940 kernel/softirq.c:288

Freed by task 3772:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:582
 slab_free_hook mm/slub.c:1355 [inline]
 slab_free_freelist_hook mm/slub.c:1377 [inline]
 slab_free mm/slub.c:2958 [inline]
 kmem_cache_free+0xbe/0x310 mm/slub.c:2980
 dst_destroy+0x200/0x360 net/core/dst.c:270
 dst_destroy_rcu+0x15/0x40 net/core/dst.c:295
 __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 __do_softirq+0x210/0x940 kernel/softirq.c:288

The buggy address belongs to the object at ffff88018e46bb40
 which belongs to the cache ip_dst_cache of size 216
The buggy address is located 24 bytes inside of
 216-byte region [ffff88018e46bb40, ffff88018e46bc18)
The buggy address belongs to the page:
page:ffffea0006391ac0 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0x8000000000000080(slab)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88018e46ba00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88018e46ba80: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
>ffff88018e46bb00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                    ^
 ffff88018e46bb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88018e46bc00: fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc
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