From 1da0b1cd4212acaeeed70a39a5a622a015bbab74 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Mateusz=20Jo=C5=84czyk?= Date: Fri, 10 Dec 2021 21:01:23 +0100 Subject: [PATCH] rtc: cmos: take rtc_lock while reading from CMOS MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit 454f47ff464325223129b9b5b8d0b61946ec704d upstream. 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 Reviewed-by: Nobuhiro Iwamatsu Cc: Alessandro Zummo Cc: Alexandre Belloni Cc: stable@vger.kernel.org Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20211210200131.153887-2-mat.jonczyk@o2.pl Signed-off-by: Greg Kroah-Hartman --- 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 c633319c..58c6382 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; -- 2.7.4