rtc: ds1307: Clamp year to valid BCD (0-99) in `set_time()`

`tm_year` may go up to 299 if the device supports the
century bit. Therefore, subtracting may not give us
a valid 2-digit number, but modulo does.

Co-developed-by: Szentendrei, Tamás <szentendrei.tamas@prolan.hu>
Signed-off-by: Szentendrei, Tamás <szentendrei.tamas@prolan.hu>
Signed-off-by: Csókás, Bence <csokas.bence@prolan.hu>
Link: https://lore.kernel.org/r/20240611072411.671600-2-csokas.bence@prolan.hu
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index bdb7b201a1605e345690f61b522a6c1af09e194f..872e0b679be4814f3108bae35395a17f5bfcd63c 100644 (file)
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -359,7 +359,7 @@ static int ds1307_set_time(struct device *dev, struct rtc_time *t)
        regs[DS1307_REG_MONTH] = bin2bcd(t->tm_mon + 1);
 
        /* assume 20YY not 19YY */
-       tmp = t->tm_year - 100;
+       tmp = t->tm_year % 100;
        regs[DS1307_REG_YEAR] = bin2bcd(tmp);
 
        if (chip->century_enable_bit)