[PATCH v2] mm/damon: validate min_region_size to be power of 2

Liew Rui Yan
2026-04-02T05:38:08Z

Problem
=======
damon_commit_ctx() checks if 'min_region_sz' is a power of 2. But if it
is not, kdamond will terminate unexpectedly due to the user's invalid
input.

Solution
========
Add the same check to damon_{lru_sort, reclaim}_apply_parameters(), but
return -EINVAL immediately. This is to prevent user's invalid input
causing kdamond to terminate unexpectedly.

This patch is a follow-up to the discussion in [1], where we agreed that
the validation should be done on min_region_sz rather than addr_unit.

[1] https://lore.kernel.org/20260330233343.4083-1-sj@kernel.org

Signed-off-by: Liew Rui Yan <aethernet65535@gmail.com>
---
Changes from v1:
- Fix memory leak issue.
- Link to v1: https://lore.kernel.org/20260331073231.30060-1-aethernet65535@gmail.com

mm/damon/lru_sort.c | 5 +++++
mm/damon/reclaim.c | 5 +++++
2 files changed, 10 insertions(+)

diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c
index 554559d72976..3fd176ef9d9c 100644
--- a/mm/damon/lru_sort.c
+++ b/mm/damon/lru_sort.c
@@ -294,6 +294,11 @@ static int damon_lru_sort_apply_parameters(void)
param_ctx->addr_unit = addr_unit;
param_ctx->min_region_sz = max(DAMON_MIN_REGION_SZ / addr_unit, 1);

+ if (!is_power_of_2(param_ctx->min_region_sz)) {
+ err = -EINVAL;
+ goto out;
+ }
+
if (!damon_lru_sort_mon_attrs.sample_interval) {
err = -EINVAL;
goto out;
diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index 86da14778658..2747eef5919d 100644
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -204,6 +204,11 @@ static int damon_reclaim_apply_parameters(void)
param_ctx->addr_unit = addr_unit;
param_ctx->min_region_sz = max(DAMON_MIN_REGION_SZ / addr_unit, 1);

+ if (!is_power_of_2(param_ctx->min_region_sz)) {
+ err = -EINVAL;
+ goto out;
+ }
+
if (!damon_reclaim_mon_attrs.aggr_interval) {
err = -EINVAL;
goto out;
--
2.53.0