[moderation] [kernel?] KCSAN: data-race in ktime_get_real_seconds / timekeeping_update_from_shadow (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a79a588fc176 Merge tag 'pm-6.16-rc5' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=154c0bd4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=eea96b85b0259840
dashboard link: https://syzkaller.appspot.com/bug?extid=235d17ec384c9409ac5e
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
CC: [jst...@google.com linux-...@vger.kernel.org sb...@kernel.org tg...@linutronix.de]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f0ea4205da34/disk-a79a588f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2b62b224950c/vmlinux-a79a588f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9341eddbbcb3/bzImage-a79a588f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+235d17...@syzkaller.appspotmail.com

==================================================================
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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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.