[moderation] [kernel?] KCSAN: data-race in hrtimer_start_range_ns / print_cpu

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5d6919055dec Linux 7.1-rc3
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11f65a73980000
kernel config: https://syzkaller.appspot.com/x/.config?x=2e40c0f41e01837e
dashboard link: https://syzkaller.appspot.com/bug?extid=bd7e9288990a753cffff
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 tg...@kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/515c0abd1a99/disk-5d691905.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3c5bf04595e0/vmlinux-5d691905.xz
kernel image: https://storage.googleapis.com/syzbot-assets/810674f82a11/bzImage-5d691905.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bd7e92...@syzkaller.appspotmail.com

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

write to 0xffff888237c1b8e8 of 8 bytes by task 3741 on cpu 0:
__hrtimer_reprogram kernel/time/hrtimer.c:713 [inline]
hrtimer_reprogram kernel/time/hrtimer.c:899 [inline]
hrtimer_start_range_ns+0xc6d/0x10a0 kernel/time/hrtimer.c:1492
hrtimer_start_expires include/linux/hrtimer.h:234 [inline]
hrtimer_restart include/linux/hrtimer.h:242 [inline]
common_hrtimer_rearm+0x85/0x90 kernel/time/posix-timers.c:296
__posixtimer_deliver_signal kernel/time/posix-timers.c:314 [inline]
posixtimer_deliver_signal+0x11f/0x300 kernel/time/posix-timers.c:340
dequeue_signal+0x2ce/0x3a0 kernel/signal.c:660
get_signal+0x375/0xf20 kernel/signal.c:2917
arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
exit_to_user_mode_loop+0x6f/0x820 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
do_syscall_64+0x232/0x3b0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888237c1b8e8 of 8 bytes by task 3728 on cpu 1:
print_cpu+0x2fb/0x670 kernel/time/timer_list.c:129
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: 0x0000000b279447ee -> 0x0000000b27940d7a

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3728 Comm: syz.3.66 Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================


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