lib: fix gmtime_assafe potential issues

Changes:
- Convert `unsigned int` to `time_t` to satisfy time truncation warnings
  even though at this point we had already used the modulus operator.

- Avoid trying to access outside the bounds of the array

  `months` array has a size of 13 elements, but the code inside the loop
  uses `i + 1` to peek on the next month.

Found by Coverity Scan (CID 1519752 and 1519769)

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/lib/zlog_5424.c b/lib/zlog_5424.c
index 9da7c55fc..60feca7fc 100644
--- a/lib/zlog_5424.c
+++ b/lib/zlog_5424.c
@@ -605,12 +605,13 @@ static void gmtime_assafe(time_t ts, struct tm *res)
 	if (ts >= 306) /* Jan 1 of next year */
 		res->tm_year++;
 
-	static unsigned int months[13] = {
+	static time_t months[13] = {
 		0, 31, 61, 92, 122, 153, 184, 214, 245, 275, 306, 337, 365,
 	};
+	const size_t month_max = array_size(months) - 1;
 
-	for (size_t i = 0; i < array_size(months); i++) {
-		if ((unsigned int)ts < months[i + 1]) {
+	for (size_t i = 0; i < month_max; i++) {
+		if (ts < months[i + 1]) {
 			res->tm_mon = ((i + 2) % 12);
 			res->tm_mday = 1 + ts - months[i];
 			break;