syzbot

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BUG: KCSAN: data-race in batadv_bla_purge_backbone_gw / batadv_bla_tx

write to 0xffff8881097fe1a0 of 8 bytes by interrupt on cpu 0:
 batadv_bla_update_own_backbone_gw net/batman-adv/bridge_loop_avoidance.c:577 [inline]
 batadv_bla_tx+0x7a6/0xc30 net/batman-adv/bridge_loop_avoidance.c:2105
 batadv_interface_tx+0x35c/0xb30 net/batman-adv/mesh-interface.c:227
 __netdev_start_xmit include/linux/netdevice.h:5222 [inline]
 netdev_start_xmit include/linux/netdevice.h:5231 [inline]
 xmit_one net/core/dev.c:3839 [inline]
 dev_hard_start_xmit+0x122/0x3e0 net/core/dev.c:3855
 __dev_queue_xmit+0x10f9/0x2000 net/core/dev.c:4725
 dev_queue_xmit include/linux/netdevice.h:3361 [inline]
 neigh_hh_output include/net/neighbour.h:531 [inline]
 neigh_output include/net/neighbour.h:545 [inline]
 ip6_finish_output2+0xa3c/0xd30 net/ipv6/ip6_output.c:141
 __ip6_finish_output net/ipv6/ip6_output.c:-1 [inline]
 ip6_finish_output+0x3a4/0x540 net/ipv6/ip6_output.c:226
 NF_HOOK_COND include/linux/netfilter.h:307 [inline]
 ip6_output+0xfd/0x240 net/ipv6/ip6_output.c:248
 dst_output include/net/dst.h:461 [inline]
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ndisc_send_skb+0x4cf/0x710 net/ipv6/ndisc.c:512
 ndisc_send_rs+0x2e7/0x360 net/ipv6/ndisc.c:722
 addrconf_rs_timer+0x1e5/0x310 net/ipv6/addrconf.c:4037
 call_timer_fn+0x38/0x2c0 kernel/time/timer.c:1747
 expire_timers kernel/time/timer.c:1798 [inline]
 __run_timers kernel/time/timer.c:2372 [inline]
 __run_timer_base+0x415/0x610 kernel/time/timer.c:2384
 run_timer_base kernel/time/timer.c:2393 [inline]
 run_timer_softirq+0x31/0x70 kernel/time/timer.c:2403
 handle_softirqs+0xb7/0x290 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0x3a/0xc0 kernel/softirq.c:680
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0x74/0x80 arch/x86/kernel/apic/apic.c:1050
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
 native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
 pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:81
 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:757
 default_idle_call+0x3d/0x70 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:190 [inline]
 do_idle+0xcb/0x240 kernel/sched/idle.c:330
 cpu_startup_entry+0x25/0x30 kernel/sched/idle.c:428
 rest_init+0xee/0xf0 init/main.c:744
 start_kernel+0x4d7/0x510 init/main.c:1097
 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:307
 x86_64_start_kernel+0xfc/0x100 arch/x86/kernel/head64.c:288
 common_startup_64+0x13e/0x147

read to 0xffff8881097fe1a0 of 8 bytes by task 3733 on cpu 1:
 batadv_bla_purge_backbone_gw+0x129/0x2d0 net/batman-adv/bridge_loop_avoidance.c:1241
 batadv_bla_periodic_work+0x103/0x580 net/batman-adv/bridge_loop_avoidance.c:1445
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x11f/0x1b0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x0000000100000c40 -> 0x0000000100001040

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3733 Comm: kworker/u8:9 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: bat_events batadv_bla_periodic_work
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