Reading from the CMOS involves writing to the index register and then
reading from the data register. Therefore access to the CMOS has to be
serialized with the rtc_lock. This invocation of CMOS_READ was not
serialized, which could cause trouble when other code is accessing CMOS
at the same time.
Use spin_lock_irq() like the rest of the function.
Nothing in kernel modifies the RTC_DM_BINARY bit, so there could be a
separate pair of spin_lock_irq() / spin_unlock_irq() before doing the
math.
Signed-off-by: Mateusz Jończyk <mat.jonczyk@xxxxx>
Reviewed-by: Nobuhiro Iwamatsu <iwamatsu@xxxxxxxxxxx>
Cc: Alessandro Zummo <a.zummo@xxxxxxxxxxxx>
Cc: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/rtc/rtc-cmos.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index 670fd8a2970e..2cd0fe728ab2 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -463,7 +463,10 @@ static int cmos_set_alarm(struct device *dev, struct rtc_wkalrm *t)
min = t->time.tm_min;
sec = t->time.tm_sec;
+ spin_lock_irq(&rtc_lock);
rtc_control = CMOS_READ(RTC_CONTROL);
+ spin_unlock_irq(&rtc_lock);
+
if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
/* Writing 0xff means "don't care" or "match all". */
mon = (mon <= 12) ? bin2bcd(mon) : 0xff;
--
2.25.1
