From 81abaeb29ed38ccbff015c98a9c6e17ca67a8375 Mon Sep 17 00:00:00 2001 From: Colin Ian King Date: Thu, 15 Feb 2018 19:36:14 +0000 Subject: rtc: tx4939: avoid unintended sign extension on a 24 bit shift [ Upstream commit 347876ad47b9923ce26e686173bbf46581802ffa ] The shifting of buf[5] by 24 bits to the left will be promoted to a 32 bit signed int and then sign-extended to an unsigned long. If the top bit of buf[5] is set then all then all the upper bits sec end up as also being set because of the sign-extension. Fix this by casting buf[5] to an unsigned long before the shift. Detected by CoverityScan, CID#1465292 ("Unintended sign extension") Fixes: 0e1492330cd2 ("rtc: add rtc-tx4939 driver") Signed-off-by: Colin Ian King Signed-off-by: Alexandre Belloni Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/rtc/rtc-tx4939.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/rtc/rtc-tx4939.c b/drivers/rtc/rtc-tx4939.c index 560d9a5e0225..a9528083061d 100644 --- a/drivers/rtc/rtc-tx4939.c +++ b/drivers/rtc/rtc-tx4939.c @@ -86,7 +86,8 @@ static int tx4939_rtc_read_time(struct device *dev, struct rtc_time *tm) for (i = 2; i < 6; i++) buf[i] = __raw_readl(&rtcreg->dat); spin_unlock_irq(&pdata->lock); - sec = (buf[5] << 24) | (buf[4] << 16) | (buf[3] << 8) | buf[2]; + sec = ((unsigned long)buf[5] << 24) | (buf[4] << 16) | + (buf[3] << 8) | buf[2]; rtc_time_to_tm(sec, tm); return rtc_valid_tm(tm); } @@ -147,7 +148,8 @@ static int tx4939_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm) alrm->enabled = (ctl & TX4939_RTCCTL_ALME) ? 1 : 0; alrm->pending = (ctl & TX4939_RTCCTL_ALMD) ? 1 : 0; spin_unlock_irq(&pdata->lock); - sec = (buf[5] << 24) | (buf[4] << 16) | (buf[3] << 8) | buf[2]; + sec = ((unsigned long)buf[5] << 24) | (buf[4] << 16) | + (buf[3] << 8) | buf[2]; rtc_time_to_tm(sec, &alrm->time); return rtc_valid_tm(&alrm->time); } -- cgit v1.2.3