syzbot

batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
batman_adv: batadv0: Interface activated: batadv_slave_0
==================================================================
BUG: KCSAN: data-race in batadv_iv_ogm_schedule / batadv_update_min_mtu

write to 0xffff8881156cd810 of 1 bytes by task 68 on cpu 0:
 batadv_iv_ogm_schedule_buff net/batman-adv/bat_iv_ogm.c:803 [inline]
 batadv_iv_ogm_schedule+0xaa/0x780 net/batman-adv/bat_iv_ogm.c:868
 batadv_iv_send_outstanding_bat_ogm_packet+0x44c/0x4b0 net/batman-adv/bat_iv_ogm.c:1712
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
 worker_thread+0x526/0x730 kernel/workqueue.c:3416
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243

read to 0xffff8881156cd810 of 1 bytes by task 3116 on cpu 1:
 batadv_hardif_min_mtu net/batman-adv/hard-interface.c:589 [inline]
 batadv_update_min_mtu+0x4b/0x180 net/batman-adv/hard-interface.c:638
 batadv_hardif_activate_interface+0x1f7/0x330 net/batman-adv/hard-interface.c:678
 batadv_hard_if_event+0x47a/0x1000 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:1950
 __dev_notify_flags+0xff/0x1a0
 dev_change_flags+0xab/0xd0 net/core/dev.c:8763
 do_setlink+0x841/0x2480 net/core/rtnetlink.c:2884
 __rtnl_newlink net/core/rtnetlink.c:3680 [inline]
 rtnl_newlink+0x11a1/0x1690 net/core/rtnetlink.c:3727
 rtnetlink_rcv_msg+0x82e/0x8e0 net/core/rtnetlink.c:6595
 netlink_rcv_skb+0x12c/0x230 net/netlink/af_netlink.c:2559
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6613
 netlink_unicast_kernel net/netlink/af_netlink.c:1335 [inline]
 netlink_unicast+0x58d/0x660 net/netlink/af_netlink.c:1361
 netlink_sendmsg+0x5d3/0x6e0 net/netlink/af_netlink.c:1905
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x140/0x180 net/socket.c:745
 __sys_sendto+0x1e5/0x260 net/socket.c:2191
 __do_sys_sendto net/socket.c:2203 [inline]
 __se_sys_sendto net/socket.c:2199 [inline]
 __x64_sys_sendto+0x78/0x90 net/socket.c:2199
 do_syscall_64+0xd3/0x1d0
 entry_SYSCALL_64_after_hwframe+0x72/0x7a

value changed: 0x04 -> 0x03

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3116 Comm: syz-executor.4 Not tainted 6.9.0-rc2-syzkaller-00040-gb1e6ec0a0fd0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
==================================================================
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3f) already exists on: batadv_slave_1
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:3f) already exists on: batadv_slave_1
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:3f) already exists on: batadv_slave_1
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:3f) 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
netdevsim netdevsim4 netdevsim0: set [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim4 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim4 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim4 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0