KCSAN: data-race in ktime_get_real_seconds / timekeeping_update_from

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in ktime_get_real_seconds / timekeeping_update_from_shadow kernel	6				1	70d	70d	0/29	auto-obsoleted due to no activity on 2025/06/27 01:56

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BUG: KCSAN: data-race in ktime_get_real_seconds / timekeeping_update_from_shadow

write to 0xffffffff88e700c8 of 280 bytes by interrupt on cpu 0:
 timekeeping_update_from_shadow+0x280/0x2b0 kernel/time/timekeeping.c:705
 timekeeping_advance+0xa07/0xba0 kernel/time/timekeeping.c:2242
 update_wall_time+0x10/0x30 kernel/time/timekeeping.c:2253
 tick_do_update_jiffies64+0x169/0x1c0 kernel/time/tick-sched.c:149
 tick_sched_do_timer kernel/time/tick-sched.c:232 [inline]
 tick_nohz_handler+0x7f/0x2d0 kernel/time/tick-sched.c:290
 __run_hrtimer kernel/time/hrtimer.c:1761 [inline]
 __hrtimer_run_queues+0x20f/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+0x5f/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
 __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:95 [inline]
 __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
 _raw_spin_unlock_irq+0x2f/0x50 kernel/locking/spinlock.c:202
 spin_unlock_irq include/linux/spinlock.h:401 [inline]
 get_signal+0xc22/0xf70 kernel/signal.c:3037
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x7a/0x100 kernel/entry/common.c:111
 exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
 do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff88e70100 of 8 bytes by task 4582 on cpu 1:
 ktime_get_real_seconds+0x15/0x30 kernel/time/timekeeping.c:965
 kmmpd+0x486/0x660 fs/ext4/mmp.c:244
 kthread+0x489/0x510 kernel/kthread.c:464
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x0000000068697577 -> 0x0000000068697578

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 4582 Comm: kmmpd-loop4 Tainted: G        W           6.16.0-rc4-syzkaller-00308-ga79a588fc176 #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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