CVE-2025-39909: Divide By Zero

In the Linux kernel, the following vulnerability has been resolved:

mm/damon/lru_sort: avoid divide-by-zero in damon_lru_sort_apply_parameters()

Patch series "mm/damon: avoid divide-by-zero in DAMON module's parameters application".

DAMON's RECLAIM and LRU_SORT modules perform no validation on user-configured parameters during application, which may lead to division-by-zero errors.

Avoid the divide-by-zero by adding validation checks when DAMON modules attempt to apply the parameters.

This patch (of 2):

During the calculation of 'hot_thres' and 'cold_thres', either 'sample_interval' or 'aggr_interval' is used as the divisor, which may lead to division-by-zero errors. Fix it by directly returning -EINVAL when such a case occurs. Additionally, since 'aggr_interval' is already required to be set no smaller than 'sample_interval' in damon_set_attrs(), only the case where 'sample_interval' is zero needs to be checked.