From: Colin Ian King Date: Tue, 28 Sep 2021 13:46:54 +0000 (+0100) Subject: rtc: msc313: Fix unintentional sign extension issues with left shift of a u16 X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=f3606687b447c41d28a011c98373b62b1cd52345;p=linux.git rtc: msc313: Fix unintentional sign extension issues with left shift of a u16 Shifting the u16 value returned by readw by 16 bits to the left will be promoted to a 32 bit signed int and then sign-extended to an unsigned long. If the top bit of the readw is set then the shifted value will be sign extended and the top 32 bits of the result will be set. Fixes: be7d9c9161b9 ("rtc: Add support for the MSTAR MSC313 RTC") Signed-off-by: Colin Ian King Reviewed-by: Romain Perier Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20210928134654.991923-1-colin.king@canonical.com --- diff --git a/drivers/rtc/rtc-msc313.c b/drivers/rtc/rtc-msc313.c index 5f178d29cfd8d..f3fde013c4b8b 100644 --- a/drivers/rtc/rtc-msc313.c +++ b/drivers/rtc/rtc-msc313.c @@ -53,7 +53,7 @@ static int msc313_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm) unsigned long seconds; seconds = readw(priv->rtc_base + REG_RTC_MATCH_VAL_L) - | (readw(priv->rtc_base + REG_RTC_MATCH_VAL_H) << 16); + | ((unsigned long)readw(priv->rtc_base + REG_RTC_MATCH_VAL_H) << 16); rtc_time64_to_tm(seconds, &alarm->time); @@ -122,7 +122,7 @@ static int msc313_rtc_read_time(struct device *dev, struct rtc_time *tm) udelay(1); seconds = readw(priv->rtc_base + REG_RTC_CNT_VAL_L) - | (readw(priv->rtc_base + REG_RTC_CNT_VAL_H) << 16); + | ((unsigned long)readw(priv->rtc_base + REG_RTC_CNT_VAL_H) << 16); rtc_time64_to_tm(seconds, tm);