[moderation] [rtc?] KCSAN: data-race in rtc_dev_poll / rtc_pie_update_irq (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d3eeb99bbc99 Merge tag 'block-6.19-20260116' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1283b522580000
kernel config: https://syzkaller.appspot.com/x/.config?x=676c6f0212d0c041
dashboard link: https://syzkaller.appspot.com/bug?extid=2d4127acca35ed7b31ad
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [alexandr...@bootlin.com linux-...@vger.kernel.org linu...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/68bc1a56de03/disk-d3eeb99b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cd8ba08f6c11/vmlinux-d3eeb99b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5277aa9db6a3/bzImage-d3eeb99b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2d4127...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in rtc_dev_poll / rtc_pie_update_irq

read-write to 0xffff88810365fb88 of 8 bytes by interrupt on cpu 1:
rtc_handle_legacy_irq drivers/rtc/interface.c:651 [inline]
rtc_pie_update_irq+0x7b/0xd0 drivers/rtc/interface.c:699
__run_hrtimer kernel/time/hrtimer.c:1777 [inline]
__hrtimer_run_queues+0x20f/0x590 kernel/time/hrtimer.c:1841
hrtimer_interrupt+0x21a/0x460 kernel/time/hrtimer.c:1903
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1045 [inline]
__sysvec_apic_timer_interrupt+0x5f/0x1d0 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_irq include/linux/spinlock_api_smp.h:160 [inline]
_raw_spin_unlock_irq+0x2f/0x50 kernel/locking/spinlock.c:202
spin_unlock_irq include/linux/spinlock.h:401 [inline]
get_signal+0xc18/0xf60 kernel/signal.c:3037
arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
exit_to_user_mode_loop+0x6a/0x6f0 kernel/entry/common.c:75
__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_work include/linux/entry-common.h:159 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
do_syscall_64+0x1d3/0x2a0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810365fb88 of 8 bytes by task 3598 on cpu 0:
rtc_dev_poll+0x78/0xb0 drivers/rtc/dev.c:198
vfs_poll include/linux/poll.h:82 [inline]
__io_arm_poll_handler+0x1ee/0xb60 io_uring/poll.c:581
io_arm_apoll+0x2eb/0x410 io_uring/poll.c:689
io_arm_poll_handler+0x131/0x160 io_uring/poll.c:718
io_queue_async+0x25d/0x2d0 io_uring/io_uring.c:2024
io_queue_sqe io_uring/io_uring.c:2050 [inline]
io_req_task_submit+0x9b/0xa0 io_uring/io_uring.c:1435
__io_run_local_work_loop io_uring/io_uring.c:1345 [inline]
__io_run_local_work+0x1f8/0x580 io_uring/io_uring.c:1370
io_run_local_work io_uring/io_uring.c:1411 [inline]
io_cqring_wait io_uring/io_uring.c:2718 [inline]
__do_sys_io_uring_enter io_uring/io_uring.c:3324 [inline]
__se_sys_io_uring_enter+0x159d/0x1c70 io_uring/io_uring.c:3224
__x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:3224
x64_sys_call+0x27e4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:427
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000000205c0 -> 0x00000000000206c0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3598 Comm: syz.1.24 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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