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authorMateusz Jończyk <mat.jonczyk@o2.pl>2021-12-10 23:01:23 +0300
committerAlexandre Belloni <alexandre.belloni@bootlin.com>2021-12-16 23:50:06 +0300
commit454f47ff464325223129b9b5b8d0b61946ec704d (patch)
treefb4b717771599a555b34dbac0b6bf74cc332c721 /drivers/rtc
parentc636783d594f6cfc95db51c796761719317ce5eb (diff)
downloadlinux-454f47ff464325223129b9b5b8d0b61946ec704d.tar.xz
rtc: cmos: take rtc_lock while reading from CMOS
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 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@o2.pl> Reviewed-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org> Cc: Alessandro Zummo <a.zummo@towertech.it> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com> Cc: stable@vger.kernel.org Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20211210200131.153887-2-mat.jonczyk@o2.pl
Diffstat (limited to 'drivers/rtc')
-rw-r--r--drivers/rtc/rtc-cmos.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index 4eb53412b808..dc3f8b0dde98 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -457,7 +457,10 @@ 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;