[moderation] [kernel?] KCSAN: data-race in __futex_wait / hrtimer_wakeup (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f0caa1d49cc0 Merge tag 'hid-for-linus-2026031701' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=106ba8da580000
kernel config: https://syzkaller.appspot.com/x/.config?x=3a78dd265deac3a9
dashboard link: https://syzkaller.appspot.com/bug?extid=3ac7e45933d94e80123b
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/623ff7afcc3c/disk-f0caa1d4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c74246446273/vmlinux-f0caa1d4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/23f07bfdfc6c/bzImage-f0caa1d4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3ac7e4...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __futex_wait / hrtimer_wakeup

read-write to 0xffffc90004ecbd80 of 8 bytes by interrupt on cpu 1:
hrtimer_wakeup+0x1c/0x50 kernel/time/hrtimer.c:2019
__run_hrtimer kernel/time/hrtimer.c:1785 [inline]
__hrtimer_run_queues+0x218/0x4f0 kernel/time/hrtimer.c:1849
hrtimer_interrupt+0x269/0x810 kernel/time/hrtimer.c:1911
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1045 [inline]
__sysvec_apic_timer_interrupt+0x5f/0x1f0 arch/x86/kernel/apic/apic.c:1062
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
sysvec_apic_timer_interrupt+0x6f/0x80 arch/x86/kernel/apic/apic.c:1056
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
__preempt_count_dec_and_test arch/x86/include/asm/preempt.h:95 [inline]
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:179 [inline]
_raw_spin_unlock_irqrestore+0x1a/0x30 kernel/locking/spinlock.c:194
spin_unlock_irqrestore include/linux/spinlock.h:407 [inline]
unlock_page_lruvec_irqrestore include/linux/memcontrol.h:1495 [inline]
folio_lruvec_relock_irqsave include/linux/memcontrol.h:1528 [inline]
folio_batch_move_lru+0x1a6/0x270 mm/swap.c:171
lru_add_drain_cpu+0x66/0x210 mm/swap.c:648
lru_add_drain mm/swap.c:737 [inline]
__folio_batch_release+0x44/0xb0 mm/swap.c:1059
folio_batch_release include/linux/pagevec.h:101 [inline]
writeback_get_folio mm/page-writeback.c:2409 [inline]
writeback_iter+0x41a/0x830 mm/page-writeback.c:2512
blkdev_writepages+0xa7/0x100 block/fops.c:485
do_writepages+0x1c6/0x310 mm/page-writeback.c:2554
filemap_writeback mm/filemap.c:387 [inline]
filemap_flush_range mm/filemap.c:436 [inline]
filemap_flush+0xee/0x130 mm/filemap.c:451
sync_blockdev_nowait+0x29/0x40 block/bdev.c:264
sync_filesystem+0xe2/0x190 fs/sync.c:60
generic_shutdown_super+0x4c/0x220 fs/super.c:625
kill_block_super+0x2a/0x70 fs/super.c:1725
deactivate_locked_super+0x75/0x1c0 fs/super.c:476
deactivate_super+0x97/0xa0 fs/super.c:509
cleanup_mnt+0x2bb/0x330 fs/namespace.c:1312
__cleanup_mnt+0x19/0x20 fs/namespace.c:1319
task_work_run+0x130/0x1a0 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
exit_to_user_mode_loop+0x1f4/0x6f0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
do_syscall_64+0x249/0x370 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffc90004ecbd80 of 8 bytes by task 10770 on cpu 0:
futex_do_wait kernel/futex/waitwake.c:357 [inline]
__futex_wait+0xee/0x260 kernel/futex/waitwake.c:687
futex_wait+0x9c/0x1d0 kernel/futex/waitwake.c:715
do_futex+0x2bf/0x380 kernel/futex/syscalls.c:130
__do_sys_futex kernel/futex/syscalls.c:207 [inline]
__se_sys_futex+0x2f6/0x370 kernel/futex/syscalls.c:188
__x64_sys_futex+0x78/0x90 kernel/futex/syscalls.c:188
x64_sys_call+0x24ab/0x3020 arch/x86/include/generated/asm/syscalls_64.h:203
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: 0xffff88811c65d3c0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 10770 Comm: syz.4.1727 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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