From: Alexandre Mergnat Date: Mon, 28 Apr 2025 10:06:48 +0000 (+0200) Subject: rtc: Fix offset calculation for .start_secs < 0 X-Git-Tag: v6.16-rc1~41^2~4 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fe9f5f96cfe8b82d0f24cbfa93718925560f4f8d;p=thirdparty%2Fkernel%2Flinux.git rtc: Fix offset calculation for .start_secs < 0 The comparison rtc->start_secs > rtc->range_max has a signed left-hand side and an unsigned right-hand side. So the comparison might become true for negative start_secs which is interpreted as a (possibly very large) positive value. As a negative value can never be bigger than an unsigned value the correct representation of the (mathematical) comparison rtc->start_secs > rtc->range_max in C is: rtc->start_secs >= 0 && rtc->start_secs > rtc->range_max Use that to fix the offset calculation currently used in the rtc-mt6397 driver. Fixes: 989515647e783 ("rtc: Add one offset seconds to expand RTC range") Signed-off-by: Alexandre Mergnat Reviewed-by: Uwe Kleine-König Link: https://lore.kernel.org/r/20250428-enable-rtc-v4-2-2b2f7e3f9349@baylibre.com Signed-off-by: Alexandre Belloni --- diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c index b88cd4fb295bc..b1a2be1f9e3b9 100644 --- a/drivers/rtc/class.c +++ b/drivers/rtc/class.c @@ -326,7 +326,7 @@ static void rtc_device_get_offset(struct rtc_device *rtc) * * Otherwise the offset seconds should be 0. */ - if (rtc->start_secs > rtc->range_max || + if ((rtc->start_secs >= 0 && rtc->start_secs > rtc->range_max) || rtc->start_secs + range_secs - 1 < rtc->range_min) rtc->offset_secs = rtc->start_secs - rtc->range_min; else if (rtc->start_secs > rtc->range_min)