Re: (sashiko review) [PATCH] mm/damon: validate addr_unit to be power of 2

[Liew Rui Yan <aethernet65535@gmail.com>]

Forwarding Sashiko review for doing discussions via mails.

# review url: https://sashiko.dev/#/patchset/20260327062627.66426-1-aethernet65535@gmail.com
# start of sashiko.dev inline review
commit ceb9522e072d53117ff67157d6f0be7d35919759
Author: Liew Rui Yan <aethernet65535@gmail.com>

mm/damon: validate addr_unit to be power of 2

This commit adds a validation check in damon_commit_ctx() to ensure
addr_unit is a power of 2. This prevents kdamond from exiting
unexpectedly during parameter application when given invalid inputs.

Link: https://lore.kernel.org/20260325025317.86571-1-sj@kernel.org

> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index db6c67e52d2b..6bad85a47a79 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c

[ ... ]

> @@ -1330,6 +1330,8 @@ int damon_commit_ctx(struct damon_ctx *dst, struct damon_ctx *src)
>  	dst->maybe_corrupted = true;
>  	if (!is_power_of_2(src->min_region_sz))
>  		return -EINVAL;
> +	if (!src->addr_unit || !is_power_of_2(src->addr_unit))

This isn't a bug, but is the !src->addr_unit check needed here?

Looking at is_power_of_2(), it already evaluates to false for an input
of zero, so the compound condition could perhaps be simplified to just
!is_power_of_2(src->addr_unit).

> +		return -EINVAL;
>  
>  	err = damon_commit_schemes(dst, src);
>  	if (err)


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