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mm/damon/lru_sort: validate min_region_size to be power of 2

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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 <aethernet65535@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Liew Rui Yan 2026-05-01 09:37:49 +08:00 committed by Andrew Morton
parent d200cfc81c
commit da7bfa6a39
1 changed files with 5 additions and 0 deletions
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5
mm/damon/lru_sort.c
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@ -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;