syzbot


KCSAN: data-race in hrtimer_reprogram / print_cpu (14)

Status: moderation: reported on 2025/08/20 21:15
Subsystems: kernel
[Documentation on labels]
Reported-by: syzbot+3aa321f3515b213afed0@syzkaller.appspotmail.com
First crash: 62d, last: 1d05h
Similar bugs (13)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu (11) kernel 6 6 479d 498d 0/29 auto-obsoleted due to no activity on 2024/08/04 04:55
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu (9) kernel 6 7 590d 645d 0/29 auto-obsoleted due to no activity on 2024/04/14 23:48
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu (13) kernel 6 1 208d 208d 0/29 auto-obsoleted due to no activity on 2025/05/23 00:02
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu (6) kernel 6 19 823d 1008d 0/29 auto-obsoleted due to no activity on 2023/08/26 13:01
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu (12) kernel 6 5 273d 352d 0/29 auto-obsoleted due to no activity on 2025/03/19 14:48
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu kernel 6 1 2042d 2042d 0/29 auto-closed as invalid on 2020/05/29 16:43
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu (2) kernel 6 1 1875d 1875d 0/29 auto-closed as invalid on 2020/10/08 05:09
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu (5) kernel 6 11 1102d 1185d 0/29 auto-obsoleted due to no activity on 2022/11/20 13:25
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu (3) kernel 6 1 1445d 1445d 0/29 auto-closed as invalid on 2021/12/12 15:07
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu (10) kernel 6 2 542d 544d 0/29 auto-obsoleted due to no activity on 2024/06/01 18:17
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu (7) kernel 6 3 777d 787d 0/29 auto-obsoleted due to no activity on 2023/10/11 12:54
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu (4) kernel 6 1 1408d 1408d 0/29 auto-closed as invalid on 2022/01/17 18:45
upstream KCSAN: data-race in hrtimer_reprogram / print_cpu (8) kernel 6 1 700d 680d 0/29 auto-obsoleted due to no activity on 2023/12/26 20:48

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

write to 0xffff888237c1b2a0 of 8 bytes by task 5020 on cpu 0:
 __hrtimer_reprogram kernel/time/hrtimer.c:656 [inline]
 hrtimer_reprogram+0x1a5/0x220 kernel/time/hrtimer.c:861
 hrtimer_start_range_ns+0x6b1/0x740 kernel/time/hrtimer.c:1323
 hrtimer_start_expires include/linux/hrtimer.h:273 [inline]
 hrtimer_restart include/linux/hrtimer.h:281 [inline]
 common_hrtimer_rearm+0x85/0x90 kernel/time/posix-timers.c:303
 __posixtimer_deliver_signal kernel/time/posix-timers.c:321 [inline]
 posixtimer_deliver_signal+0x120/0x320 kernel/time/posix-timers.c:347
 dequeue_signal+0x2cf/0x3b0 kernel/signal.c:660
 get_signal+0x376/0xf70 kernel/signal.c:2914
 arch_do_signal_or_restart+0x96/0x440 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x77/0x110 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888237c1b2a0 of 8 bytes by task 5016 on cpu 1:
 print_cpu+0x2ea/0x660 kernel/time/timer_list.c:131
 timer_list_show+0x107/0x170 kernel/time/timer_list.c:293
 seq_read_iter+0x636/0x950 fs/seq_file.c:272
 proc_reg_read_iter+0x110/0x180 fs/proc/inode.c:299
 copy_splice_read+0x442/0x660 fs/splice.c:363
 do_splice_read fs/splice.c:982 [inline]
 splice_direct_to_actor+0x26f/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+0x2bb4/0x3000 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: 0x00000010651d79ad -> 0x00000010651019dc

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 5016 Comm: syz.4.578 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
==================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/21 11:08 upstream 6548d364a3e8 9832ed61 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in hrtimer_reprogram / print_cpu
2025/10/12 15:04 upstream 67029a49db6c ff1712fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in hrtimer_reprogram / print_cpu
2025/09/09 10:31 upstream f777d1112ee5 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in hrtimer_reprogram / print_cpu
2025/09/05 02:50 upstream 08b06c30a445 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in hrtimer_reprogram / print_cpu
2025/08/20 21:14 upstream b19a97d57c15 0b9605c8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in hrtimer_reprogram / print_cpu
* Struck through repros no longer work on HEAD.