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BUG: KASAN: use-after-free in fib6_ifdown+0x82b/0x8b0 net/ipv6/route.c:3659
Read of size 8 at addr ffff8801d3e1a980 by task kworker/u4:0/5

CPU: 1 PID: 5 Comm: kworker/u4:0 Not tainted 4.15.0-rc7-mm1+ #54
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 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+0x23b/0x360 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 fib6_ifdown+0x82b/0x8b0 net/ipv6/route.c:3659
 fib6_clean_node+0x389/0x580 net/ipv6/ip6_fib.c:1912
 fib6_walk_continue+0x46c/0x8a0 net/ipv6/ip6_fib.c:1838
 fib6_walk+0x91/0xf0 net/ipv6/ip6_fib.c:1886
 fib6_clean_tree+0x1e6/0x340 net/ipv6/ip6_fib.c:1963
 __fib6_clean_all+0x1f4/0x3a0 net/ipv6/ip6_fib.c:1979
 fib6_clean_all+0x27/0x30 net/ipv6/ip6_fib.c:1990
 rt6_sync_down_dev net/ipv6/route.c:3698 [inline]
 rt6_disable_ip+0xfd/0x700 net/ipv6/route.c:3703
 addrconf_ifdown+0x14b/0x14f0 net/ipv6/addrconf.c:3595
 addrconf_notify+0x5f8/0x2310 net/ipv6/addrconf.c:3519
 notifier_call_chain+0x136/0x2c0 kernel/notifier.c:93
 __raw_notifier_call_chain kernel/notifier.c:394 [inline]
 raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
 call_netdevice_notifiers_info+0x32/0x70 net/core/dev.c:1708
 call_netdevice_notifiers net/core/dev.c:1726 [inline]
 netdev_wait_allrefs+0x229/0x410 net/core/dev.c:7998
 netdev_run_todo+0x478/0xae0 net/core/dev.c:8089
 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:108
 sit_exit_batch_net+0x4ce/0x720 net/ipv6/sit.c:1873
 ops_exit_list.isra.6+0x100/0x150 net/core/net_namespace.c:145
 cleanup_net+0x5c7/0xb50 net/core/net_namespace.c:484
 process_one_work+0xbbf/0x1af0 kernel/workqueue.c:2112
 worker_thread+0x223/0x1990 kernel/workqueue.c:2246
 kthread+0x33c/0x400 kernel/kthread.c:238
 ret_from_fork+0x4b/0x60 arch/x86/entry/entry_64.S:547

Allocated by task 12154:
 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
 __ip6_dst_alloc+0x35/0x90 net/ipv6/route.c:361
 ip6_dst_alloc+0x29/0xb0 net/ipv6/route.c:376
 ip6_route_info_create+0x4ff/0x2e20 net/ipv6/route.c:2538
 ip6_route_add+0xa2/0x190 net/ipv6/route.c:2779
 ipv6_route_ioctl+0x4db/0x6b0 net/ipv6/route.c:3299
 inet6_ioctl+0xef/0x1e0 net/ipv6/af_inet6.c:520
 sock_do_ioctl+0x65/0xb0 net/socket.c:956
 sock_ioctl+0x2c2/0x440 net/socket.c:1053
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 19646:
 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+0x86/0x2b0 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 ffff8801d3e1a980
 which belongs to the cache ip6_dst_cache of size 320
The buggy address is located 0 bytes inside of
 320-byte region [ffff8801d3e1a980, ffff8801d3e1aac0)
The buggy address belongs to the page:
page:ffffea00074f8680 count:1 mapcount:0 mapping:ffff8801d3e1a080 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d3e1a080 0000000000000000 000000010000000a
raw: ffffea0006f426e0 ffffea0006f29020 ffff8801d2c0e6c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d3e1a880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d3e1a900: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff8801d3e1a980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8801d3e1aa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d3e1aa80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
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