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BUG: KCSAN: data-race in batadv_hardif_activate_interface / batadv_mcast_mla_update

write to 0xffff888168057a10 of 1 bytes by task 30711 on cpu 1:
 batadv_hardif_activate_interface+0x99/0x330 net/batman-adv/hard-interface.c:666
 batadv_hard_if_event+0x47a/0x1010 net/batman-adv/hard-interface.c:977
 notifier_call_chain kernel/notifier.c:93 [inline]
 raw_notifier_call_chain+0x6f/0x1d0 kernel/notifier.c:461
 call_netdevice_notifiers_info+0xae/0x100 net/core/dev.c:1996
 __dev_notify_flags+0xff/0x1a0
 dev_change_flags+0xab/0xd0 net/core/dev.c:8914
 do_setlink+0x844/0x2490 net/core/rtnetlink.c:2900
 __rtnl_newlink net/core/rtnetlink.c:3696 [inline]
 rtnl_newlink+0x11a3/0x1690 net/core/rtnetlink.c:3743
 rtnetlink_rcv_msg+0x6aa/0x710 net/core/rtnetlink.c:6646
 netlink_rcv_skb+0x12c/0x230 net/netlink/af_netlink.c:2550
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6664
 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
 netlink_unicast+0x599/0x670 net/netlink/af_netlink.c:1357
 netlink_sendmsg+0x5cc/0x6e0 net/netlink/af_netlink.c:1901
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x140/0x180 net/socket.c:745
 __sys_sendto+0x1d6/0x260 net/socket.c:2210
 __do_sys_sendto net/socket.c:2222 [inline]
 __se_sys_sendto net/socket.c:2218 [inline]
 __x64_sys_sendto+0x78/0x90 net/socket.c:2218
 x64_sys_call+0x2959/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888168057a10 of 1 bytes by task 2338 on cpu 0:
 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: 0x02 -> 0x04

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2338 Comm: kworker/u8:11 Tainted: G        W          6.11.0-syzkaller-09959-gabf2050f51fd #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Workqueue: bat_events batadv_mcast_mla_update

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