[moderation] [kernel?] KCSAN: data-race in print_cpu / tick_nohz_idle_enter (12)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4ee64205ffaa Merge tag 'clk-for-linus' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=149c0cce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=ff1bc04bab908995
dashboard link: https://syzkaller.appspot.com/bug?extid=93d60d8165f31d9da6aa
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [anna-...@linutronix.de fred...@kernel.org linux-...@vger.kernel.org mi...@kernel.org tg...@kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e2ff5e3f4a08/disk-4ee64205.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/65d8a395837c/vmlinux-4ee64205.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a5fd2c472bcd/bzImage-4ee64205.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+93d60d...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in print_cpu / tick_nohz_idle_enter

write to 0xffff888237c1bf28 of 8 bytes by task 0 on cpu 0:
tick_nohz_start_idle kernel/time/tick-sched.c:779 [inline]
tick_nohz_idle_enter+0x92/0xf0 kernel/time/tick-sched.c:1307
do_idle+0x3b/0x2b0 kernel/sched/idle.c:298
cpu_startup_entry+0x24/0x30 kernel/sched/idle.c:451
rest_init+0xee/0xf0 init/main.c:762
start_kernel+0x49f/0x4d0 init/main.c:1220
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
x86_64_start_kernel+0xfc/0x100 arch/x86/kernel/head64.c:291
common_startup_64+0x13e/0x147

read to 0xffff888237c1bf28 of 8 bytes by task 9982 on cpu 1:
print_cpu+0x4ef/0x670 kernel/time/timer_list.c:158
timer_list_show+0x107/0x170 kernel/time/timer_list.c:291
seq_read_iter+0x636/0x940 fs/seq_file.c:273
proc_reg_read_iter+0x110/0x180 fs/proc/inode.c:299
copy_splice_read+0x471/0x6c0 fs/splice.c:362
do_splice_read fs/splice.c:980 [inline]
splice_direct_to_actor+0x26e/0x670 fs/splice.c:1084
do_splice_direct_actor fs/splice.c:1202 [inline]
do_splice_direct+0x119/0x1a0 fs/splice.c:1228
do_sendfile+0x382/0x650 fs/read_write.c:1372
__do_sys_sendfile64 fs/read_write.c:1433 [inline]
__se_sys_sendfile64 fs/read_write.c:1419 [inline]
__x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1419
x64_sys_call+0x2dc4/0x3020 arch/x86/include/generated/asm/syscalls_64.h:41
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: 0x0000006517af19da -> 0x0000006517b10e84

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 9982 Comm: syz.0.1858 Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
==================================================================


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