On 15/02/18 18:59, Colin King wrote:
> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxx>
> ---
> drivers/rtc/rtc-tx4939.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/rtc/rtc-tx4939.c b/drivers/rtc/rtc-tx4939.c
> index feededce3ded..b8a066cbcc42 100644
> --- a/drivers/rtc/rtc-tx4939.c
> +++ b/drivers/rtc/rtc-tx4939.c
> @@ -170,7 +170,8 @@ 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);
> }
>
Nack, there are two occurrences of this sign extension, I missed the
other one. I'll re-send a fix.
Colin
