Fix sdlog2/logger path/file name overflows. (#5138)

* logger: prevent logpath buffer overflows

The handling of the log path had the potential to cause buffer
overflows, especially on POSIX platforms where the paths are often much
longer than just 64 chars.

* sdlog2: prevent logpath buffer overflows

When the log folder path was created, this was done with the unsafe
sprintf function instead of snprintf. This caused buffer overflows in
SITL but the overflow was usually not detected until recent testing of
some work in progress.

src/modules/logger/logger.cpp

@@ -860,6 +860,12 @@ int Logger::create_log_dir(tm *tt)
 
 	if (tt) {
 		int n = snprintf(_log_dir, sizeof(_log_dir), "%s/", LOG_ROOT);
+
+		if (n >= sizeof(_log_dir)) {
+			PX4_ERR("log path too long");
+			return -1;
+		}
+
 		strftime(_log_dir + n, sizeof(_log_dir) - n, "%Y-%m-%d", tt);
 		mkdir_ret = mkdir(_log_dir, S_IRWXU | S_IRWXG | S_IRWXO);
 
@@ -874,7 +880,13 @@ int Logger::create_log_dir(tm *tt)
 		/* look for the next dir that does not exist */
 		while (!_has_log_dir && dir_number <= MAX_NO_LOGFOLDER) {
 			/* format log dir: e.g. /fs/microsd/sess001 */
-			sprintf(_log_dir, "%s/sess%03u", LOG_ROOT, dir_number);
+			int n = snprintf(_log_dir, sizeof(_log_dir), "%s/sess%03u", LOG_ROOT, dir_number);
+
+			if (n >= sizeof(_log_dir)) {
+				PX4_ERR("log path too long");
+				return -1;
+			}
+
 			mkdir_ret = mkdir(_log_dir, S_IRWXU | S_IRWXG | S_IRWXO);
 
 			if (mkdir_ret == 0) {
@@ -1030,7 +1042,7 @@ void Logger::start_log()
 
 	PX4_INFO("start log");
 
-	char file_name[64] = "";
+	char file_name[LOG_DIR_LEN] = "";
 
 	if (get_log_file_name(file_name, sizeof(file_name))) {
 		PX4_ERR("logger: failed to get log file name");