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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4f79eaa2ceac kbuild: Properly disable -Wunterminated-strin..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16f73774580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6bd11c5d4ce102b4
dashboard link: https://syzkaller.appspot.com/bug?extid=ff96813529cd8174ae6e
compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
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/f1b0b4c83f04/disk-4f79eaa2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/84acac77c2b8/vmlinux-4f79eaa2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2b3765a19582/bzImage-4f79eaa2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ff9681...@syzkaller.appspotmail.com

netdevsim netdevsim4 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim4 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim4 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
==================================================================
BUG: KCSAN: data-race in ktime_get_real_seconds / timekeeping_update_from_shadow

write to 0xffffffff88e4e0c8 of 280 bytes by interrupt on cpu 1:
timekeeping_update_from_shadow+0x280/0x2b0 kernel/time/timekeeping.c:680
timekeeping_advance+0x9b5/0xb50 kernel/time/timekeeping.c:2208
update_wall_time+0x10/0x30 kernel/time/timekeeping.c:2219
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+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:1038 [inline]
__sysvec_apic_timer_interrupt+0x5c/0x1d0 arch/x86/kernel/apic/apic.c:1055
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
sysvec_apic_timer_interrupt+0x6f/0x80 arch/x86/kernel/apic/apic.c:1049
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
should_watch kernel/kcsan/core.c:280 [inline]
check_access kernel/kcsan/core.c:752 [inline]
__tsan_read4+0x118/0x190 kernel/kcsan/core.c:1024
selinux_socket_unix_may_send+0xc6/0x130 security/selinux/hooks.c:5111
security_unix_may_send+0x40/0x80 security/security.c:4536
unix_dgram_sendmsg+0x795/0xec0 net/unix/af_unix.c:2105
sock_sendmsg_nosec net/socket.c:712 [inline]
__sock_sendmsg+0x142/0x180 net/socket.c:727
____sys_sendmsg+0x345/0x4e0 net/socket.c:2566
___sys_sendmsg+0x17b/0x1d0 net/socket.c:2620
__sys_sendmmsg+0x178/0x300 net/socket.c:2709
__do_sys_sendmmsg net/socket.c:2736 [inline]
__se_sys_sendmmsg net/socket.c:2733 [inline]
__x64_sys_sendmmsg+0x57/0x70 net/socket.c:2733
x64_sys_call+0x2f2f/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:308
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff88e4e100 of 8 bytes by task 31391 on cpu 0:
ktime_get_real_seconds+0x15/0x30 kernel/time/timekeeping.c:939
mnt_warn_timestamp_expiry+0x9c/0x200 fs/namespace.c:3271
do_new_mount_fc fs/namespace.c:3819 [inline]
do_new_mount+0x2f6/0x680 fs/namespace.c:3886
path_mount+0x4a4/0xb20 fs/namespace.c:4211
do_mount fs/namespace.c:4224 [inline]
__do_sys_mount fs/namespace.c:4435 [inline]
__se_sys_mount+0x28f/0x2e0 fs/namespace.c:4412
__x64_sys_mount+0x67/0x80 fs/namespace.c:4412
x64_sys_call+0xd36/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:166
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000000150a7b9 -> 0x000000000150a7ba

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 31391 Comm: syz-executor Not tainted 6.15.0-rc4-syzkaller-00052-g4f79eaa2ceac #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
==================================================================


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[syzbot]

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