rtc: hctosys: Add missing range error reporting

BugLink: https://bugs.launchpad.net/bugs/1810947

commit 7ce9a992 upstream.

Fix an issue with the 32-bit range error path in `rtc_hctosys' where no
error code is set and consequently the successful preceding call result
from `rtc_read_time' is propagated to `rtc_hctosys_ret'.  This in turn
makes any subsequent call to `hctosys_show' incorrectly report in sysfs
that the system time has been set from this RTC while it has not.

Set the error to ERANGE then if we can't express the result due to an
overflow.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Fixes: b3a5ac42 ("rtc: hctosys: Ensure system time doesn't overflow time_t")
Cc: stable@vger.kernel.org # 4.17+
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/rtc/hctosys.c

@@ -50,8 +50,10 @@ static int __init rtc_hctosys(void)
 	tv64.tv_sec = rtc_tm_to_time64(&tm);
 
 #if BITS_PER_LONG == 32
-	if (tv64.tv_sec > INT_MAX)
+	if (tv64.tv_sec > INT_MAX) {
+		err = -ERANGE;
 		goto err_read;
+	}
 #endif
 
 	err = do_settimeofday64(&tv64);