I found data-race in my fuzzer:

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

write to 0xffff88800b307380 of 8 bytes by interrupt on cpu 1: rtc_handle_legacy_irq+0x58/0xb0 drivers/rtc/interface.c:624 rtc_pie_update_irq+0x75/0x90 drivers/rtc/interface.c:672 __run_hrtimer kernel/time/hrtimer.c:1761 [inline] __hrtimer_run_queues+0x2c4/0x5d0 kernel/time/hrtimer.c:1825 hrtimer_interrupt+0x214/0x4a0 kernel/time/hrtimer.c:1887 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1038 [inline] ....

read to 0xffff88800b307380 of 8 bytes by task 11566 on cpu 0: rtc_dev_poll+0x6c/0xa0 drivers/rtc/dev.c:198 vfs_poll include/linux/poll.h:82 [inline] select_poll_one fs/select.c:480 [inline] do_select+0x95f/0x1030 fs/select.c:536 core_sys_select+0x284/0x6d0 fs/select.c:677 do_pselect.constprop.0+0x118/0x150 fs/select.c:759 ....

value changed: 0x00000000000801c0 -> 0x00000000000802c0 ==================================================================

rtc_dev_poll() is reading rtc->irq_data without a spinlock for some unknown reason. This causes a data-race, so we need to add a spinlock to fix it.

Cc: stable@vger.kernel.org Fixes: e824290e5dcf ("[PATCH] RTC subsystem: dev interface") Signed-off-by: Jeongjun Park aha310510@gmail.com --- drivers/rtc/dev.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/drivers/rtc/dev.c b/drivers/rtc/dev.c index 0eeae5bcc3aa..a6570a5a938a 100644 --- a/drivers/rtc/dev.c +++ b/drivers/rtc/dev.c @@ -195,7 +195,9 @@ static __poll_t rtc_dev_poll(struct file *file, poll_table *wait)

poll_wait(file, &rtc->irq_queue, wait);

+ spin_lock_irq(&rtc->irq_lock); data = rtc->irq_data; + spin_unlock_irq(&rtc->irq_lock);

return (data != 0) ? (EPOLLIN | EPOLLRDNORM) : 0; } --