From 00b912b0c88e690b1662067497182454357b18b0 Mon Sep 17 00:00:00 2001 From: Daniel Axtens Date: Tue, 15 Dec 2015 18:09:14 +1100 Subject: powerpc: Remove broken GregorianDay() GregorianDay() is supposed to calculate the day of the week (tm->tm_wday) for a given day/month/year. In that calcuation it indexed into an array called MonthOffset using tm->tm_mon-1. However tm_mon is zero-based, not one-based, so this is off-by-one. It also means that every January, GregoiranDay() will access element -1 of the MonthOffset array. It also doesn't appear to be a correct algorithm either: see in contrast kernel/time/timeconv.c's time_to_tm function. It's been broken forever, which suggests no-one in userland uses this. It looks like no-one in the kernel uses tm->tm_wday either (see e.g. drivers/rtc/rtc-ds1305.c:319). tm->tm_wday is conventionally set to -1 when not available in hardware so we can simply set it to -1 and drop the function. (There are over a dozen other drivers in drivers/rtc that do this.) Found using UBSAN. Cc: Andrey Ryabinin Cc: Andrew Morton # as an example of what UBSan finds. Cc: Alessandro Zummo Cc: Alexandre Belloni Cc: rtc-linux@googlegroups.com Signed-off-by: Daniel Axtens Acked-by: Alexandre Belloni Signed-off-by: Michael Ellerman --- drivers/rtc/rtc-opal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/rtc') diff --git a/drivers/rtc/rtc-opal.c b/drivers/rtc/rtc-opal.c index df39ce02a99d..9c18d6fd8107 100644 --- a/drivers/rtc/rtc-opal.c +++ b/drivers/rtc/rtc-opal.c @@ -40,7 +40,7 @@ static void opal_to_tm(u32 y_m_d, u64 h_m_s_ms, struct rtc_time *tm) tm->tm_min = bcd2bin((h_m_s_ms >> 48) & 0xff); tm->tm_sec = bcd2bin((h_m_s_ms >> 40) & 0xff); - GregorianDay(tm); + tm->tm_wday = -1; } static void tm_to_opal(struct rtc_time *tm, u32 *y_m_d, u64 *h_m_s_ms) -- cgit v1.2.3