syzbot


KCSAN: data-race in print_cpu / tick_nohz_idle_stop_tick

Status: moderation: reported on 2025/09/08 11:35
Subsystems: kernel
[Documentation on labels]
Reported-by: syzbot+1810c74ddb4c43db6bdc@syzkaller.appspotmail.com
First crash: 3d22h, last: 3d22h

Sample crash report:
==================================================================
BUG: KCSAN: data-race in print_cpu / tick_nohz_idle_stop_tick

read-write to 0xffff888237d1b868 of 8 bytes by task 0 on cpu 1:
 tick_nohz_idle_stop_tick+0x145/0x790 kernel/time/tick-sched.c:1222
 cpuidle_idle_call kernel/sched/idle.c:188 [inline]
 do_idle+0xc6/0x240 kernel/sched/idle.c:330
 cpu_startup_entry+0x25/0x30 kernel/sched/idle.c:428
 start_secondary+0x95/0xa0 arch/x86/kernel/smpboot.c:315
 common_startup_64+0x13e/0x147

read to 0xffff888237d1b868 of 8 bytes by task 22203 on cpu 0:
 print_cpu+0x4b0/0x680 kernel/time/timer_list.c:160
 timer_list_show+0x107/0x170 kernel/time/timer_list.c:295
 seq_read_iter+0x316/0x940 fs/seq_file.c:230
 proc_reg_read_iter+0x110/0x180 fs/proc/inode.c:299
 copy_splice_read+0x43f/0x660 fs/splice.c:363
 do_splice_read fs/splice.c:982 [inline]
 splice_direct_to_actor+0x26c/0x680 fs/splice.c:1086
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 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+0x2bb0/0x2ff0 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: 0x00000000000d9471 -> 0x00000000000d9472

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 22203 Comm: syz.2.15300 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/08 11:35 upstream 76eeb9b8de98 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in print_cpu / tick_nohz_idle_stop_tick
* Struck through repros no longer work on HEAD.