Description:

When running admin/cron.php with stats generation, the while in stats_cron_monthly() in lib/statslib.php runs into a infinite loop and fills up the server space with junks in database (stats_monthly table).

Affected setup:

This bug affects servers in negative timezones with the correct local time set, but choose a negative GMT number in the timezone option under Variables in Administration.

(bug does not affect negative timezone servers with timezone set to Server's local time)

Action:

running admin/cron.php (manually or scheduled)

Coniditions:

• The stats_daily, stats_weekly, and stats_monthly tables do not contain any previously created data (empty tables).

• Administration/Configuration/Variables/Interface/timezone is set to a negative GMT.

• Administration/Configuration/Variables/Statistics/enablestats is set to Yes

• Administration/Configuration/Variables/Statistics/statsfirstrun is set to start at a time that's in the last month

• Administration/Configuration/Variables/Statistics/statsmaxruntime is set to Until complete (might not have an effect on this bug?)

Furthur observation:

In stats_getdate() in lib/statslib.php, after the

$time += intval((float)$timezone * HOURSECS);

timezone adjustment, any negative timezone will be returned as an earlier time. This leads back to the while infinite loop in stats_cron_monthly():

while ($monthend >= $nextmonthend) {

Since nextmonthend is alwasys the same and smaller than monthend, this loop never ends. Server CPU goes 100%, database gets filled with junk data, all kind of wonderful things happen.

Suggested Fix:

• User: the timezone option should be set to Server's local time if the server is not using GMT(0).

• Moodle: better description for the timezone option? additional server timezone check in statslib?