==================================================================
BUG: KCSAN: data-race in ktime_get_mono_fast_ns / update_fast_timekeeper

write to 0xffffffff86d4fb48 of 56 bytes by interrupt on cpu 1:
 update_fast_timekeeper+0x38/0x70 kernel/time/timekeeping.c:476
 timekeeping_update_from_shadow+0x3ab/0x440 kernel/time/timekeeping.c:812
 __timekeeping_advance+0xa5d/0xc10 kernel/time/timekeeping.c:2532
 timekeeping_advance kernel/time/timekeeping.c:2540 [inline]
 update_wall_time+0x21/0x50 kernel/time/timekeeping.c:2550
 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+0x8d/0x3d0 kernel/time/tick-sched.c:312
 __run_hrtimer kernel/time/hrtimer.c:1930 [inline]
 __hrtimer_run_queues+0x276/0x4f0 kernel/time/hrtimer.c:1994
 hrtimer_interrupt+0x261/0x850 kernel/time/hrtimer.c:2113
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 __sysvec_apic_timer_interrupt+0x5f/0x1c0 arch/x86/kernel/apic/apic.c:1067
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
 sysvec_apic_timer_interrupt+0x6f/0x80 arch/x86/kernel/apic/apic.c:1061
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
 kcsan_setup_watchpoint+0x1/0x410 kernel/kcsan/core.c:528
 folio_next_index include/linux/pagemap.h:946 [inline]
 filemap_map_pages+0x375/0xea0 mm/filemap.c:3928
 do_fault_around mm/memory.c:5867 [inline]
 do_read_fault mm/memory.c:5900 [inline]
 do_fault mm/memory.c:6043 [inline]
 do_pte_missing mm/memory.c:4566 [inline]
 handle_pte_fault mm/memory.c:6427 [inline]
 __handle_mm_fault mm/memory.c:6565 [inline]
 handle_mm_fault+0x1508/0x2e70 mm/memory.c:6734
 faultin_page mm/gup.c:1126 [inline]
 __get_user_pages+0x1290/0x1f10 mm/gup.c:1428
 populate_vma_page_range mm/gup.c:1860 [inline]
 __mm_populate+0x242/0x390 mm/gup.c:1963
 mm_populate include/linux/mm.h:4137 [inline]
 vm_mmap_pgoff+0x23b/0x2d0 mm/util.c:586
 ksys_mmap_pgoff+0xc1/0x310 mm/mmap.c:606
 x64_sys_call+0x14df/0x3020 arch/x86/include/generated/asm/syscalls_64.h:10
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86d4fb68 of 8 bytes by task 6043 on cpu 0:
 timekeeping_cycles_to_ns kernel/time/timekeeping.c:444 [inline]
 timekeeping_get_ns kernel/time/timekeeping.c:449 [inline]
 __ktime_get_fast_ns kernel/time/timekeeping.c:497 [inline]
 ktime_get_mono_fast_ns+0xdf/0x1a0 kernel/time/timekeeping.c:537
 ____bpf_ktime_get_ns kernel/bpf/helpers.c:181 [inline]
 bpf_ktime_get_ns+0xe/0x20 kernel/bpf/helpers.c:178
 bpf_prog_3aa7d5b0ccc3ba5f+0x48/0x50
 bpf_dispatcher_nop_func include/linux/bpf.h:1402 [inline]
 __bpf_prog_run include/linux/filter.h:722 [inline]
 bpf_prog_run include/linux/filter.h:729 [inline]
 bpf_prog_run_pin_on_cpu include/linux/filter.h:746 [inline]
 bpf_flow_dissect+0x158/0x350 net/core/flow_dissector.c:1024
 bpf_prog_test_run_flow_dissector+0x25d/0x360 net/bpf/test_run.c:1525
 bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4742
 __sys_bpf+0x52e/0x7e0 kernel/bpf/syscall.c:6292
 __do_sys_bpf kernel/bpf/syscall.c:6387 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6385 [inline]
 __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6385
 x64_sys_call+0x10cb/0x3020 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00020ae66381d4a0 -> 0x0002a37ce3b13866

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6043 Comm: syz.2.782 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================