syzbot

batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
batman_adv: batadv0: Interface activated: batadv_slave_1
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BUG: KCSAN: data-race in batadv_iv_ogm_schedule / batadv_update_min_mtu

write to 0xffff8880b2586210 of 1 bytes by task 7 on cpu 0:
 batadv_iv_ogm_schedule_buff net/batman-adv/bat_iv_ogm.c:803 [inline]
 batadv_iv_ogm_schedule+0xb3/0x790 net/batman-adv/bat_iv_ogm.c:869
 batadv_iv_send_outstanding_bat_ogm_packet+0x451/0x4b0 net/batman-adv/bat_iv_ogm.c:1723
 process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x20d/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff8880b2586210 of 1 bytes by task 8739 on cpu 1:
 batadv_hardif_min_mtu net/batman-adv/hard-interface.c:576 [inline]
 batadv_update_min_mtu+0x49/0x1a0 net/batman-adv/hard-interface.c:621
 batadv_hardif_activate_interface+0x1cf/0x2e0 net/batman-adv/hard-interface.c:653
 batadv_hard_if_event+0x2e4/0xc70 net/batman-adv/hard-interface.c:1043
 notifier_call_chain kernel/notifier.c:83 [inline]
 __raw_notifier_call_chain kernel/notifier.c:361 [inline]
 raw_notifier_call_chain+0x53/0xb0 kernel/notifier.c:368
 __dev_notify_flags+0x1cd/0x390 net/core/dev.c:2033
 dev_change_flags+0xa2/0xc0 net/core/dev.c:8361
 do_setlink+0x736/0x2220 net/core/rtnetlink.c:2706
 __rtnl_newlink net/core/rtnetlink.c:3374 [inline]
 rtnl_newlink+0xe62/0x1340 net/core/rtnetlink.c:3500
 rtnetlink_rcv_msg+0x71b/0x7b0 net/core/rtnetlink.c:5563
 netlink_rcv_skb+0x13e/0x240 net/netlink/af_netlink.c:2470
 rtnetlink_rcv+0x18/0x20 net/core/rtnetlink.c:5581
 netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
 netlink_unicast+0x5e2/0x6b0 net/netlink/af_netlink.c:1330
 netlink_sendmsg+0x6d8/0x7a0 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg net/socket.c:671 [inline]
 __sys_sendto+0x2ae/0x380 net/socket.c:1992
 __do_sys_sendto net/socket.c:2004 [inline]
 __se_sys_sendto net/socket.c:2000 [inline]
 __x64_sys_sendto+0x74/0x90 net/socket.c:2000
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8739 Comm: syz-executor.1 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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