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BUG: KCSAN: data-race in ktime_get_mono_fast_ns / update_fast_timekeeper

write to 0xffffffff86f4fcc8 of 56 bytes by interrupt on cpu 0:
 update_fast_timekeeper+0x38/0x70 kernel/time/timekeeping.c:509
 timekeeping_update_from_shadow+0x3c0/0x480 kernel/time/timekeeping.c:845
 __timekeeping_advance+0xb36/0xcf0 kernel/time/timekeeping.c:2663
 timekeeping_advance kernel/time/timekeeping.c:2671 [inline]
 update_wall_time+0x21/0x50 kernel/time/timekeeping.c:2681
 tick_do_update_jiffies64+0x169/0x1c0 kernel/time/tick-sched.c:149
 tick_sched_do_timer kernel/time/tick-sched.c:253 [inline]
 tick_nohz_handler+0x88/0x380 kernel/time/tick-sched.c:310
 __run_hrtimer kernel/time/hrtimer.c:2067 [inline]
 __hrtimer_run_queues+0x1f8/0x510 kernel/time/hrtimer.c:2124
 hrtimer_interrupt+0x27b/0x860 kernel/time/hrtimer.c:2243
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
 __sysvec_apic_timer_interrupt+0x5f/0x1c0 arch/x86/kernel/apic/apic.c:1068
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0x6f/0x80 arch/x86/kernel/apic/apic.c:1062
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
 kcsan_setup_watchpoint+0x42b/0x4a0 kernel/kcsan/core.c:713
 __tlb_remove_folio_pages_size mm/mmu_gather.c:-1 [inline]
 __tlb_remove_folio_pages+0x61/0x220 mm/mmu_gather.c:210
 zap_present_folio_ptes mm/memory.c:1808 [inline]
 zap_present_ptes mm/memory.c:1861 [inline]
 do_zap_pte_range mm/memory.c:1963 [inline]
 zap_pte_range mm/memory.c:2065 [inline]
 zap_pmd_range mm/memory.c:2151 [inline]
 zap_pud_range mm/memory.c:2179 [inline]
 zap_p4d_range mm/memory.c:2200 [inline]
 __zap_vma_range+0x1597/0x2ce0 mm/memory.c:2240
 unmap_vmas+0x200/0x310 mm/memory.c:2309
 exit_mmap+0x1a2/0x5e0 mm/mmap.c:1315
 __mmput+0x28/0x1c0 kernel/fork.c:1193
 mmput+0x40/0x50 kernel/fork.c:1216
 exit_mm+0x113/0x1a0 kernel/exit.c:614
 do_exit+0x438/0x1510 kernel/exit.c:996
 do_group_exit+0xfe/0x140 kernel/exit.c:1151
 get_signal+0xe07/0xf10 kernel/signal.c:3039
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x15d/0x8c0 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
 do_syscall_64+0x212/0x360 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86f4fce8 of 8 bytes by task 19701 on cpu 1:
 timekeeping_cycles_to_ns kernel/time/timekeeping.c:477 [inline]
 timekeeping_get_ns kernel/time/timekeeping.c:482 [inline]
 __ktime_get_fast_ns kernel/time/timekeeping.c:530 [inline]
 ktime_get_mono_fast_ns+0xdf/0x1a0 kernel/time/timekeeping.c:570
 ktime_get_boot_fast_ns+0xf/0x40 kernel/time/timekeeping.c:614
 ____bpf_ktime_get_boot_ns kernel/bpf/helpers.c:193 [inline]
 bpf_ktime_get_boot_ns+0xe/0x20 kernel/bpf/helpers.c:190
 bpf_prog_de3ce70f1ff88a64+0x23/0x29
 bpf_dispatcher_xdp_func+0x25/0x30 net/core/filter.c:12186
 __bpf_prog_run include/linux/filter.h:779 [inline]
 bpf_prog_run_xdp include/net/xdp.h:696 [inline]
 bpf_test_run+0x231/0x620 net/bpf/test_run.c:420
 bpf_prog_test_run_xdp+0x587/0x9e0 net/bpf/test_run.c:1465
 bpf_prog_test_run+0x208/0x340 kernel/bpf/syscall.c:4804
 __sys_bpf+0x8da/0xc30 kernel/bpf/syscall.c:6385
 __do_sys_bpf kernel/bpf/syscall.c:6486 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6483 [inline]
 __x64_sys_bpf+0x69/0x80 kernel/bpf/syscall.c:6483
 x64_sys_call+0xf26/0x2550 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x003b365be993ed31 -> 0x00003bca56ba8334

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 19701 Comm: syz.0.7829 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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