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

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Problem
=======
When a user sets an invalid 'addr_unit' (e.g., 3) via 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.

Reproduction
============
1. Enable DAMON_RECLAIM
2. Set addr_unit=3
3. Commit inputs via 'commit_inputs'
4. Observe kdamond termination

Solution
========
Add an early validation in 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.

Link: https://lore.kernel.org/20260501013750.71704-3-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 09:37:50 +08:00 committed by Andrew Morton
parent da7bfa6a39
commit d52c1331d2
1 changed files with 5 additions and 0 deletions
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5
mm/damon/reclaim.c
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@ -210,6 +210,11 @@ 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;