| From: Colin Ian King <colin.king@canonical.com> |
| Date: Thu, 15 Feb 2018 19:36:14 +0000 |
| Subject: rtc: tx4939: avoid unintended sign extension on a 24 bit shift |
| |
| commit 347876ad47b9923ce26e686173bbf46581802ffa upstream. |
| |
| 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 <colin.king@canonical.com> |
| Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| drivers/rtc/rtc-tx4939.c | 6 ++++-- |
| 1 file changed, 4 insertions(+), 2 deletions(-) |
| |
| --- a/drivers/rtc/rtc-tx4939.c |
| +++ b/drivers/rtc/rtc-tx4939.c |
| @@ -86,7 +86,8 @@ static int tx4939_rtc_read_time(struct d |
| 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 |
| 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); |
| } |