Re: [PATCH] system/rtc: Silent overflow in qemu_timedate_diff()

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

ping?

On 11/8/25 12:08, Philippe Mathieu-Daudé wrote:
> Per ctime(3) man-page:
> 
>    A negative value for tm_isdst causes the mktime() function to
>    attempt to divine whether summer time is in effect for the
>    specified time.  The tm_isdst and tm_gmtoff members are forced
>    to zero by timegm().
> 
>    The mktime() function returns the specified calendar time; if
>    the calendar time cannot be represented, it returns -1;
> 
> Coverity reports (CID 1547724 Overflowed return value) the
> qemu_timedate_diff() method doesn't handle this error path.
> 
> Since this method was added in commit f650305967f ("Unify RTCs
> that use host time, fix M48t59 alarm") in 2008, and there is no
> open issue related to it, keep ignoring this unlikely case, but
> add an assertion to make Coverity happy.
> 
> Fixes: CID 1547724
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   system/rtc.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/system/rtc.c b/system/rtc.c
> index 56951288c40..070b99fe6ad 100644
> --- a/system/rtc.c
> +++ b/system/rtc.c
> @@ -98,6 +98,7 @@ time_t qemu_timedate_diff(struct tm *tm)
>           struct tm tmp = *tm;
>           tmp.tm_isdst = -1; /* use timezone to figure it out */
>           seconds = mktime(&tmp);
> +        assert(seconds >= 0);
>           break;
>       }
>       default: