[moderation] [kernel?] KCSAN: data-race in print_cpu / tick_nohz_idle_enter (11)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 038d61fd6422 Linux 6.16
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17cd1034580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8dc7678a542ae3e3
dashboard link: https://syzkaller.appspot.com/bug?extid=1d852428b8cd11950088
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
CC: [anna-...@linutronix.de fred...@kernel.org linux-...@vger.kernel.org mi...@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/6a76508f8501/disk-038d61fd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/532f76ae58b5/vmlinux-038d61fd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c2acfae736a7/bzImage-038d61fd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1d8524...@syzkaller.appspotmail.com

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

write to 0xffff888237c1b830 of 8 bytes by task 0 on cpu 0:
tick_nohz_start_idle kernel/time/tick-sched.c:748 [inline]
tick_nohz_idle_enter+0x89/0xe0 kernel/time/tick-sched.c:1264
do_idle+0x3d/0x240 kernel/sched/idle.c:271
cpu_startup_entry+0x25/0x30 kernel/sched/idle.c:423
rest_init+0xee/0xf0 init/main.c:745
start_kernel+0x592/0x600 init/main.c:1102
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:307
x86_64_start_kernel+0xfc/0x100 arch/x86/kernel/head64.c:288
common_startup_64+0x13e/0x147

read to 0xffff888237c1b830 of 8 bytes by task 7960 on cpu 1:
print_cpu+0x502/0x680 kernel/time/timer_list.c:162
timer_list_show+0x107/0x170 kernel/time/timer_list.c:295
seq_read_iter+0x62a/0x940 fs/seq_file.c:272
proc_reg_read_iter+0x110/0x180 fs/proc/inode.c:299
copy_splice_read+0x3c4/0x5f0 fs/splice.c:363
do_splice_read fs/splice.c:979 [inline]
splice_direct_to_actor+0x26f/0x680 fs/splice.c:1083
do_splice_direct_actor fs/splice.c:1201 [inline]
do_splice_direct+0xda/0x150 fs/splice.c:1227
do_sendfile+0x380/0x650 fs/read_write.c:1370
__do_sys_sendfile64 fs/read_write.c:1431 [inline]
__se_sys_sendfile64 fs/read_write.c:1417 [inline]
__x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
x64_sys_call+0xb39/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:41
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000016750281ff -> 0x00000016750427fd

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 7960 Comm: syz.0.1687 Not tainted 6.16.0-syzkaller #0 PREEMPT(voluntary)
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.