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BUG: KCSAN: data-race in batadv_hard_if_event / batadv_mcast_mla_update

write to 0xffff88811d0f8a10 of 1 bytes by task 5495 on cpu 0:
 batadv_hardif_remove_interface net/batman-adv/hard-interface.c:930 [inline]
 batadv_hard_if_event+0x896/0xfb0 net/batman-adv/hard-interface.c:988
 notifier_call_chain kernel/notifier.c:85 [inline]
 raw_notifier_call_chain+0x6f/0x1d0 kernel/notifier.c:453
 call_netdevice_notifiers_info+0xae/0x100 net/core/dev.c:1996
 call_netdevice_notifiers_extack net/core/dev.c:2034 [inline]
 call_netdevice_notifiers net/core/dev.c:2048 [inline]
 unregister_netdevice_many_notify+0x8b7/0x11b0 net/core/dev.c:11526
 unregister_netdevice_many+0x19/0x20 net/core/dev.c:11590
 cleanup_net+0x417/0x860 net/core/net_namespace.c:643
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3310
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3391
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffff88811d0f8a10 of 1 bytes by task 5500 on cpu 1:
 batadv_mcast_mla_forw_flags_get net/batman-adv/multicast.c:253 [inline]
 batadv_mcast_mla_flags_get net/batman-adv/multicast.c:290 [inline]
 __batadv_mcast_mla_update net/batman-adv/multicast.c:910 [inline]
 batadv_mcast_mla_update+0x21b/0x1700 net/batman-adv/multicast.c:949
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3310
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3391
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 5500 Comm: kworker/u8:27 Not tainted 6.13.0-rc5-syzkaller-00006-g56e6a3499e14 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: bat_events batadv_mcast_mla_update
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