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BUG: KCSAN: data-race in batadv_hardif_disable_interface.cold / batadv_iv_ogm_schedule_buff

write to 0xffff8880a46a6470 of 8 bytes by task 17706 on cpu 1:
 batadv_hardif_disable_interface.cold+0x3e7/0x55e net/batman-adv/hard-interface.c:895
 batadv_softif_destroy_netlink+0x7e/0xe0 net/batman-adv/soft-interface.c:1113
 default_device_exit_batch+0x1a1/0x260 net/core/dev.c:10447
 ops_exit_list.isra.0+0x9e/0xb0 net/core/net_namespace.c:175
 cleanup_net+0x40a/0x6a0 net/core/net_namespace.c:589
 process_one_work+0x424/0x930 kernel/workqueue.c:2264
 worker_thread+0x9a/0x7e0 kernel/workqueue.c:2410
 kthread+0x1cb/0x1f0 kernel/kthread.c:255
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff8880a46a6470 of 8 bytes by task 16561 on cpu 0:
 batadv_iv_ogm_schedule_buff+0x5b6/0x840 net/batman-adv/bat_iv_ogm.c:839
 batadv_iv_ogm_schedule net/batman-adv/bat_iv_ogm.c:865 [inline]
 batadv_iv_ogm_schedule net/batman-adv/bat_iv_ogm.c:858 [inline]
 batadv_iv_send_outstanding_bat_ogm_packet+0x20c/0x510 net/batman-adv/bat_iv_ogm.c:1718
 process_one_work+0x424/0x930 kernel/workqueue.c:2264
 worker_thread+0x9a/0x7e0 kernel/workqueue.c:2410
 kthread+0x1cb/0x1f0 kernel/kthread.c:255
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 16561 Comm: kworker/u4:7 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: bat_events batadv_iv_send_outstanding_bat_ogm_packet
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