5.4-stable review patch. If anyone has any objections, please let me know.
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From: Alexandre Mergnat amergnat@baylibre.com
[ Upstream commit fe9f5f96cfe8b82d0f24cbfa93718925560f4f8d ]
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 amergnat@baylibre.com Reviewed-by: Uwe Kleine-König u.kleine-koenig@baylibre.com Link: https://lore.kernel.org/r/20250428-enable-rtc-v4-2-2b2f7e3f9349@baylibre.com Signed-off-by: Alexandre Belloni alexandre.belloni@bootlin.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/rtc/class.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c index 8b434213bc7ad..87cb34acadde3 100644 --- a/drivers/rtc/class.c +++ b/drivers/rtc/class.c @@ -270,7 +270,7 @@ 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)