6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: SeongJae Park <sj@xxxxxxxxxx> commit 3bafc47d3c4a2fc4d3b382aeb3c087f8fc84d9fd upstream. When calculating the hotness of each region for the under-quota regions prioritization, DAMON divides some values by the maximum nr_accesses. However, due to the type of the related variables, simple division-based calculation of the divisor can return zero. As a result, divide-by-zero is possible. Fix it by using damon_max_nr_accesses(), which handles the case. Link: https://lkml.kernel.org/r/20231019194924.100347-4-sj@xxxxxxxxxx Fixes: 198f0f4c58b9 ("mm/damon/vaddr,paddr: support pageout prioritization") Signed-off-by: SeongJae Park <sj@xxxxxxxxxx> Reported-by: Jakub Acs <acsjakub@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [5.16+] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/damon/ops-common.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) --- a/mm/damon/ops-common.c +++ b/mm/damon/ops-common.c @@ -87,7 +87,6 @@ void damon_pmdp_mkold(pmd_t *pmd, struct int damon_hot_score(struct damon_ctx *c, struct damon_region *r, struct damos *s) { - unsigned int max_nr_accesses; int freq_subscore; unsigned int age_in_sec; int age_in_log, age_subscore; @@ -95,8 +94,8 @@ int damon_hot_score(struct damon_ctx *c, unsigned int age_weight = s->quota.weight_age; int hotness; - max_nr_accesses = c->attrs.aggr_interval / c->attrs.sample_interval; - freq_subscore = r->nr_accesses * DAMON_MAX_SUBSCORE / max_nr_accesses; + freq_subscore = r->nr_accesses * DAMON_MAX_SUBSCORE / + damon_max_nr_accesses(&c->attrs); age_in_sec = (unsigned long)r->age * c->attrs.aggr_interval / 1000000; for (age_in_log = 0; age_in_log < DAMON_MAX_AGE_IN_LOG && age_in_sec;
