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BUG: KCSAN: data-race in rtc_dev_poll / rtc_pie_update_irq

read-write to 0xffff8881033d2b88 of 8 bytes by interrupt on cpu 1:
 rtc_handle_legacy_irq drivers/rtc/interface.c:624 [inline]
 rtc_pie_update_irq+0x93/0xf0 drivers/rtc/interface.c:672
 __run_hrtimer kernel/time/hrtimer.c:1761 [inline]
 __hrtimer_run_queues+0x20c/0x5a0 kernel/time/hrtimer.c:1825
 hrtimer_interrupt+0x21a/0x460 kernel/time/hrtimer.c:1887
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1039 [inline]
 __sysvec_apic_timer_interrupt+0x5c/0x1d0 arch/x86/kernel/apic/apic.c:1056
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0x6f/0x80 arch/x86/kernel/apic/apic.c:1050
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
 kcsan_setup_watchpoint+0x415/0x430 kernel/kcsan/core.c:705
 stack_trace_consume_entry+0x6d/0xc0 kernel/stacktrace.c:93
 arch_stack_walk+0x10d/0x150 arch/x86/kernel/stacktrace.c:27
 stack_trace_save+0x5e/0x90 kernel/stacktrace.c:122
 ref_tracker_free+0x94/0x3e0 lib/ref_tracker.c:307
 netdev_tracker_free include/linux/netdevice.h:4369 [inline]
 netdev_put include/linux/netdevice.h:4386 [inline]
 in6_dev_finish_destroy+0x7c/0x150 net/ipv6/addrconf_core.c:273
 in6_dev_put include/net/addrconf.h:417 [inline]
 addrconf_ifdown+0xe1b/0xf30 net/ipv6/addrconf.c:4009
 addrconf_notify+0x222/0x930 net/ipv6/addrconf.c:-1
 notifier_call_chain kernel/notifier.c:85 [inline]
 raw_notifier_call_chain+0x6c/0x1b0 kernel/notifier.c:453
 call_netdevice_notifiers_info+0xae/0x100 net/core/dev.c:2229
 call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
 call_netdevice_notifiers net/core/dev.c:2281 [inline]
 unregister_netdevice_many_notify+0xda9/0x15d0 net/core/dev.c:12166
 unregister_netdevice_many+0x19/0x20 net/core/dev.c:12229
 ops_exit_rtnl_list net/core/net_namespace.c:186 [inline]
 ops_undo_list+0x213/0x410 net/core/net_namespace.c:247
 cleanup_net+0x2de/0x4d0 net/core/net_namespace.c:682
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 kernel/kthread.c:463
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff8881033d2b88 of 8 bytes by task 7080 on cpu 0:
 rtc_dev_poll+0x78/0xb0 drivers/rtc/dev.c:198
 vfs_poll include/linux/poll.h:82 [inline]
 io_file_supports_nowait io_uring/rw.c:46 [inline]
 __io_read+0x2e4/0xc20 io_uring/rw.c:927
 io_read+0x1c/0x60 io_uring/rw.c:1020
 __io_issue_sqe+0xfe/0x2e0 io_uring/io_uring.c:1773
 io_issue_sqe+0x53/0x970 io_uring/io_uring.c:1796
 io_queue_sqe io_uring/io_uring.c:2025 [inline]
 io_req_task_submit+0x6b/0xd0 io_uring/io_uring.c:1415
 io_handle_tw_list+0x190/0x1c0 io_uring/io_uring.c:1102
 tctx_task_work_run+0x6d/0x1a0 io_uring/io_uring.c:1167
 tctx_task_work+0x3f/0x80 io_uring/io_uring.c:1185
 task_work_run+0x131/0x1a0 kernel/task_work.c:227
 get_signal+0xe13/0xf70 kernel/signal.c:2807
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x7a/0x100 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000000065c0 -> 0x00000000000066c0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 7080 Comm: syz.5.1404 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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