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BUG: KASAN: use-after-free in ip6_dst_idev include/net/ip6_fib.h:192 [inline]
BUG: KASAN: use-after-free in ip6_xmit+0x1f76/0x2260 net/ipv6/ip6_output.c:264
Read of size 8 at addr ffff8801bb802918 by task syz-executor0/17209

CPU: 0 PID: 17209 Comm: syz-executor0 Not tainted 4.16.0-rc4+ #269
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23c/0x360 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 ip6_dst_idev include/net/ip6_fib.h:192 [inline]
 ip6_xmit+0x1f76/0x2260 net/ipv6/ip6_output.c:264
 inet6_csk_xmit+0x2fc/0x580 net/ipv6/inet6_connection_sock.c:139
 l2tp_xmit_core net/l2tp/l2tp_core.c:1053 [inline]
 l2tp_xmit_skb+0x105f/0x1410 net/l2tp/l2tp_core.c:1148
 pppol2tp_sendmsg+0x470/0x670 net/l2tp/l2tp_ppp.c:341
 sock_sendmsg_nosec net/socket.c:629 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:639
 SYSC_sendto+0x361/0x5c0 net/socket.c:1748
 SyS_sendto+0x40/0x50 net/socket.c:1716
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x453e69
RSP: 002b:00007f9a7e6d9c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f9a7e6da6d4 RCX: 0000000000453e69
RDX: 000000000000100b RSI: 0000000020001180 RDI: 0000000000000014
RBP: 000000000072bea0 R08: 00000000200021c0 R09: 0000000000000080
R10: 0000000000040001 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000004ca R14: 00000000006f7390 R15: 0000000000000000

Allocated by task 13461:
 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:552
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3541
 dst_alloc+0x11f/0x1a0 net/core/dst.c:104
 rt_dst_alloc+0xe9/0x4e0 net/ipv4/route.c:1508
 ip_route_input_slow+0x1284/0x3c80 net/ipv4/route.c:2014
 ip_route_input_rcu+0xf1/0xd20 net/ipv4/route.c:2143
 ip_route_input_noref+0xf5/0x1e0 net/ipv4/route.c:2089
 ip_rcv_finish+0x3a6/0x2040 net/ipv4/ip_input.c:348
 NF_HOOK include/linux/netfilter.h:288 [inline]
 ip_rcv+0xb76/0x1820 net/ipv4/ip_input.c:493
 __netif_receive_skb_core+0x1a41/0x3460 net/core/dev.c:4557
 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4622
 netif_receive_skb_internal+0x10b/0x670 net/core/dev.c:4696
 netif_receive_skb+0xae/0x390 net/core/dev.c:4720
 tun_rx_batched.isra.52+0x5ee/0x870 drivers/net/tun.c:1555
 tun_get_user+0x25a5/0x3810 drivers/net/tun.c:1959
 tun_chr_write_iter+0xb9/0x160 drivers/net/tun.c:1987
 call_write_iter include/linux/fs.h:1781 [inline]
 do_iter_readv_writev+0x55c/0x830 fs/read_write.c:653
 do_iter_write+0x154/0x540 fs/read_write.c:932
 vfs_writev+0x18a/0x340 fs/read_write.c:977
 do_writev+0xfc/0x2a0 fs/read_write.c:1012
 SYSC_writev fs/read_write.c:1085 [inline]
 SyS_writev+0x27/0x30 fs/read_write.c:1082
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 13452:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3485 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3743
 dst_destroy+0x257/0x370 net/core/dst.c:140
 dst_destroy_rcu+0x16/0x20 net/core/dst.c:153
 __rcu_reclaim kernel/rcu/rcu.h:172 [inline]
 rcu_do_batch kernel/rcu/tree.c:2674 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2933 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2900 [inline]
 rcu_process_callbacks+0xd6c/0x17f0 kernel/rcu/tree.c:2917
 __do_softirq+0x2d7/0xb85 kernel/softirq.c:285

The buggy address belongs to the object at ffff8801bb802900
 which belongs to the cache ip_dst_cache of size 160
The buggy address is located 24 bytes inside of
 160-byte region [ffff8801bb802900, ffff8801bb8029a0)
The buggy address belongs to the page:
page:ffffea0006ee0080 count:1 mapcount:0 mapping:ffff8801bb802000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bb802000 0000000000000000 0000000100000010
raw: ffffea000719d1e0 ffffea0006d57920 ffff8801d5b90e00 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bb802800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801bb802880: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801bb802900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff8801bb802980: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801bb802a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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