[moderation] [kernel?] KCSAN: data-race in hrtimer_reprogram / print_cpu (15)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 631919fb12fe Merge tag 'sched_ext-for-7.0-rc6-fixes-2' of ..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=123b1516580000
kernel config: https://syzkaller.appspot.com/x/.config?x=3a78dd265deac3a9
dashboard link: https://syzkaller.appspot.com/bug?extid=29307e428930f695b90c
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/06a44f7e7477/disk-631919fb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/84e0dab112bd/vmlinux-631919fb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/528169471198/bzImage-631919fb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+29307e...@syzkaller.appspotmail.com

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

write to 0xffff888237d1b8a0 of 8 bytes by task 11557 on cpu 1:
__hrtimer_reprogram kernel/time/hrtimer.c:664 [inline]
hrtimer_reprogram+0x1a5/0x220 kernel/time/hrtimer.c:869
hrtimer_start_range_ns+0xd0f/0x10f0 kernel/time/hrtimer.c:1331
hrtimer_start_expires include/linux/hrtimer.h:258 [inline]
hrtimer_sleeper_start_expires kernel/time/hrtimer.c:2047 [inline]
do_nanosleep+0x78/0x330 kernel/time/hrtimer.c:2121
hrtimer_nanosleep+0x207/0x3e0 kernel/time/hrtimer.c:2171
common_nsleep+0x62/0x80 kernel/time/posix-timers.c:1345
__do_sys_clock_nanosleep kernel/time/posix-timers.c:1391 [inline]
__se_sys_clock_nanosleep+0x223/0x260 kernel/time/posix-timers.c:1368
__x64_sys_clock_nanosleep+0x55/0x70 kernel/time/posix-timers.c:1368
x64_sys_call+0x146e/0x3020 arch/x86/include/generated/asm/syscalls_64.h:231
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888237d1b8a0 of 8 bytes by task 11603 on cpu 0:
print_cpu+0x2ea/0x660 kernel/time/timer_list.c:131
timer_list_show+0x107/0x170 kernel/time/timer_list.c:293
seq_read_iter+0x31e/0x940 fs/seq_file.c:231
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/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000003c55f29900 -> 0x0000003c55e5de1b

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 11603 Comm: syz.1.1902 Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================


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