From: Liew Rui Yan Date: Fri, 1 May 2026 01:37:49 +0000 (+0800) Subject: mm/damon/lru_sort: validate min_region_size to be power of 2 X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=da7bfa6a39fd4d72e03b6bc5f01148ac22fd216e;p=thirdparty%2Flinux.git mm/damon/lru_sort: validate min_region_size to be power of 2 Patch series "mm/damon: validate min_region_size to be power of 2", v5. Problem ======= When a user sets an invalid 'addr_unit' (e.g., 3) via DAMON_LRU_SORT or DAMON_RECLAIM, 'min_region_sz' becomes a non-power-of-2 value. While damon_commit_ctx() correctly detects this and returns -EINVAL, it sets the 'maybe_corrupted' flag during this process. This flag causes the running kdamond to terminate. While the termination is a safety measure, it is suboptimal in this case because the error is just a simple invalid input from the user, which shouldn't neccessitate stopping the kdamond. Solution ======== Add an early validation in damon_lru_sort_apply_parameters() and damon_reclaim_apply_parameters() to check 'min_region_sz' before any state change occurs. If it is non-power-of-2, return -EINVAL immediately, preventing 'maybe_corrupted' from being set. Patch 1 fixes the issue for DAMON_LRU_SORT. Patch 2 fixes the issue for DAMON_RECLAIM. This patch (of 2): Problem ======= When a user sets an invalid 'addr_unit' (e.g., 3) via DAMON_LRU_SORT, 'min_region_sz' becomes a non-power-of-2 value. While damon_commit_ctx() correctly detects this and returns -EINVAL, it sets the 'maybe_corrupted' flag during this process. This flag causes the running kdamond to terminate. While the termination is a safety measure, it is suboptimal in this case because the error is just a simple invalid input from the user, which shouldn't neccessitate stopping the kdamond. Reproduction ============ 1. Enable DAMON_LRU_SORT 2. Set addr_unit=3 3. Commit inputs via 'commit_inputs' 4. Observe kdamond termination Solution ======== Add an early validation in damon_lru_sort_apply_parameters() to check 'min_region_sz' before any state change occurs. If it is non-power-of-2, return -EINVAL immediately, preventing 'maybe_corrupted' from being set. Link: https://lore.kernel.org/20260501013750.71704-1-aethernet65535@gmail.com Link: https://lore.kernel.org/20260501013750.71704-2-aethernet65535@gmail.com Signed-off-by: Liew Rui Yan Reviewed-by: SeongJae Park Signed-off-by: Andrew Morton --- diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c index 2eb559d913b6..eca88ed941b3 100644 --- a/mm/damon/lru_sort.c +++ b/mm/damon/lru_sort.c @@ -286,6 +286,11 @@ 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;