syzbot

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BUG: KASAN: user-memory-access in fib6_drop_pcpu_from net/ipv6/ip6_fib.c:921 [inline]
BUG: KASAN: user-memory-access in fib6_purge_rt+0x1b3/0x5e0 net/ipv6/ip6_fib.c:933
Write of size 8 at addr 0000000000004d38 by task kworker/u4:9/19107

CPU: 1 PID: 19107 Comm: kworker/u4:9 Not tainted 5.2.0-rc3+ #47
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:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 __kasan_report.cold+0x5/0x40 mm/kasan/report.c:321
 kasan_report+0x12/0x20 mm/kasan/common.c:614
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x123/0x190 mm/kasan/generic.c:191
 kasan_check_write+0x14/0x20 mm/kasan/common.c:100
 fib6_drop_pcpu_from net/ipv6/ip6_fib.c:921 [inline]
 fib6_purge_rt+0x1b3/0x5e0 net/ipv6/ip6_fib.c:933
 fib6_del_route net/ipv6/ip6_fib.c:1808 [inline]
 fib6_del+0xac2/0x10a0 net/ipv6/ip6_fib.c:1839
 fib6_clean_node+0x3a5/0x590 net/ipv6/ip6_fib.c:2001
 fib6_walk_continue+0x4a9/0x8e0 net/ipv6/ip6_fib.c:1923
 fib6_walk+0x9d/0x100 net/ipv6/ip6_fib.c:1971
 fib6_clean_tree+0xe0/0x120 net/ipv6/ip6_fib.c:2050
 __fib6_clean_all+0x118/0x2a0 net/ipv6/ip6_fib.c:2066
 fib6_clean_all+0x2b/0x40 net/ipv6/ip6_fib.c:2077
 rt6_sync_down_dev+0x134/0x150 net/ipv6/route.c:4165
 rt6_disable_ip+0x27/0x5f0 net/ipv6/route.c:4170
 addrconf_ifdown+0xa2/0x1220 net/ipv6/addrconf.c:3705
 addrconf_notify+0x5db/0x2270 net/ipv6/addrconf.c:3630
 notifier_call_chain+0xc2/0x230 kernel/notifier.c:95
 __raw_notifier_call_chain kernel/notifier.c:396 [inline]
 raw_notifier_call_chain+0x2e/0x40 kernel/notifier.c:403
 call_netdevice_notifiers_info+0x3f/0x90 net/core/dev.c:1749
 call_netdevice_notifiers_extack net/core/dev.c:1761 [inline]
 call_netdevice_notifiers net/core/dev.c:1775 [inline]
 dev_close_many+0x33f/0x6f0 net/core/dev.c:1518
 rollback_registered_many+0x43b/0xfc0 net/core/dev.c:8155
 unregister_netdevice_many.part.0+0x1b/0x1f0 net/core/dev.c:9286
 unregister_netdevice_many+0x3b/0x50 net/core/dev.c:9285
 sit_exit_batch_net+0x560/0x750 net/ipv6/sit.c:1891
 ops_exit_list.isra.0+0xfc/0x150 net/core/net_namespace.c:157
 cleanup_net+0x3fb/0x960 net/core/net_namespace.c:553
 process_one_work+0x989/0x1790 kernel/workqueue.c:2269
 worker_thread+0x98/0xe40 kernel/workqueue.c:2415
 kthread+0x354/0x420 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
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