==================================================================
BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_unless include/linux/atomic-fallback.h:1086 [inline]
BUG: KASAN: use-after-free in atomic_add_unless include/linux/atomic-fallback.h:1111 [inline]
BUG: KASAN: use-after-free in atomic_inc_not_zero include/linux/atomic-fallback.h:1127 [inline]
BUG: KASAN: use-after-free in dst_hold_safe include/net/dst.h:297 [inline]
BUG: KASAN: use-after-free in ip6_hold_safe+0xad/0x380 net/ipv6/route.c:1046
Read of size 4 at addr ffff888093c4dec4 by task kworker/u4:10/10202

CPU: 1 PID: 10202 Comm: kworker/u4:10 Not tainted 5.2.0-rc3+ #51
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:188
 __kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
 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_read+0x11/0x20 mm/kasan/common.c:94
 atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
 atomic_fetch_add_unless include/linux/atomic-fallback.h:1086 [inline]
 atomic_add_unless include/linux/atomic-fallback.h:1111 [inline]
 atomic_inc_not_zero include/linux/atomic-fallback.h:1127 [inline]
 dst_hold_safe include/net/dst.h:297 [inline]
 ip6_hold_safe+0xad/0x380 net/ipv6/route.c:1046
 rt6_get_pcpu_route net/ipv6/route.c:1273 [inline]
 ip6_pol_route+0x339/0x1050 net/ipv6/route.c:1952
 ip6_pol_route_output+0x54/0x70 net/ipv6/route.c:2128
 fib6_rule_lookup+0x133/0x5a0 net/ipv6/fib6_rules.c:116
 ip6_route_output_flags+0x2c4/0x350 net/ipv6/route.c:2157
 ip6_route_output include/net/ip6_route.h:89 [inline]
 icmpv6_xrlim_allow+0x11e/0x440 net/ipv6/icmp.c:208
 icmp6_send+0x1145/0x1e90 net/ipv6/icmp.c:541
 icmpv6_send+0xec/0x230 net/ipv6/ip6_icmp.c:43
 ip6_link_failure+0x2b/0x530 net/ipv6/route.c:2291
 dst_link_failure include/net/dst.h:416 [inline]
 ndisc_error_report+0xce/0x1c0 net/ipv6/ndisc.c:708
 neigh_invalidate+0x245/0x570 net/core/neighbour.c:994
 neigh_timer_handler+0xc33/0xf30 net/core/neighbour.c:1080
 call_timer_fn+0x193/0x720 kernel/time/timer.c:1322
 expire_timers kernel/time/timer.c:1366 [inline]
 __run_timers kernel/time/timer.c:1685 [inline]
 __run_timers kernel/time/timer.c:1653 [inline]
 run_timer_softirq+0x66f/0x1740 kernel/time/timer.c:1698
 __do_softirq+0x25c/0x94c kernel/softirq.c:293
 invoke_softirq kernel/softirq.c:374 [inline]
 irq_exit+0x180/0x1d0 kernel/softirq.c:414
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0x13b/0x550 arch/x86/kernel/apic/apic.c:1068
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:806
 </IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:767 [inline]
RIP: 0010:lock_acquire+0x1ea/0x3f0 kernel/locking/lockdep.c:4306
Code: 7c 08 00 00 00 00 00 00 48 c1 e8 03 80 3c 10 00 0f 85 c4 01 00 00 48 83 3d 72 07 5b 07 00 0f 84 38 01 00 00 48 8b 7d c8 57 9d <0f> 1f 44 00 00 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 65 8b
RSP: 0018:ffff8880625ffb10 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff1164e7e RBX: ffff8880626343c0 RCX: ffff888062634c40
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: 0000000000000286
RBP: ffff8880625ffb58 R08: 00000000edd98333 R09: ffff888062634cd8
R10: ffff888062634cb8 R11: ffff8880626343c0 R12: ffffffff88ba3580
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000002
 rcu_lock_acquire include/linux/rcupdate.h:208 [inline]
 rcu_read_lock include/linux/rcupdate.h:593 [inline]
 inet_twsk_purge+0xc0/0x5f0 net/ipv4/inet_timewait_sock.c:268
 tcp_sk_exit_batch+0x22/0xa0 net/ipv4/tcp_ipv4.c:2715
 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

The buggy address belongs to the page:
page:ffffea00024f1340 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x1fffc0000000000()
raw: 01fffc0000000000 0000000000000000 ffffea00024f1308 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888093c4dd80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888093c4de00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888093c4de80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff888093c4df00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888093c4df80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================