[moderation] [kernel?] KCSAN: data-race in print_cpu / tick_nohz_idle_enter (10)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cf87f46fd34d Merge tag 'drm-fixes-2024-05-11' of https://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15f7996c980000
kernel config: https://syzkaller.appspot.com/x/.config?x=168fab99759dff68
dashboard link: https://syzkaller.appspot.com/bug?extid=dbec1d508021c2bd1bfd
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
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/19ced7c04631/disk-cf87f46f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5cc9ad64696b/vmlinux-cf87f46f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/51408b47f6e5/bzImage-cf87f46f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dbec1d...@syzkaller.appspotmail.com

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

read-write to 0xffff888237c204b8 of 8 bytes by task 0 on cpu 0:
tick_sched_flag_set kernel/time/tick-sched.c:194 [inline]
tick_nohz_idle_enter+0x59/0xe0 kernel/time/tick-sched.c:1262
do_idle+0x3d/0x230 kernel/sched/idle.c:277
cpu_startup_entry+0x25/0x30 kernel/sched/idle.c:430
rest_init+0xef/0xf0 init/main.c:739
start_kernel+0x57c/0x5e0 init/main.c:1081
x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:507
x86_64_start_kernel+0x94/0xa0 arch/x86/kernel/head64.c:488
common_startup_64+0x12c/0x137

read to 0xffff888237c204b8 of 8 bytes by task 12702 on cpu 1:
print_cpu+0x3dd/0x670 kernel/time/timer_list.c:155
timer_list_show+0x115/0x180 kernel/time/timer_list.c:295
seq_read_iter+0x65b/0x940 fs/seq_file.c:272
proc_reg_read_iter+0x11e/0x190 fs/proc/inode.c:299
call_read_iter include/linux/fs.h:2104 [inline]
copy_splice_read+0x3a4/0x5d0 fs/splice.c:365
do_splice_read fs/splice.c:985 [inline]
splice_direct_to_actor+0x26c/0x670 fs/splice.c:1089
do_splice_direct_actor fs/splice.c:1207 [inline]
do_splice_direct+0xd7/0x150 fs/splice.c:1233
do_sendfile+0x3b9/0x970 fs/read_write.c:1295
__do_sys_sendfile64 fs/read_write.c:1362 [inline]
__se_sys_sendfile64 fs/read_write.c:1348 [inline]
__x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1348
x64_sys_call+0x2c67/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:41
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000030 -> 0x0000000000000035

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 12702 Comm: syz-executor.4 Not tainted 6.9.0-rc7-syzkaller-00183-gcf87f46fd34d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup