# Re: \[PATCH 6/7\] lkdtm: crash on overwriting protected pmalloc var

- From: J Freyensee \<hidden\>
- Date: 2018-03-06 17:05:00 
- List: linux-mm
- Page: https://ratatoskr.run/linux-mm/2018/03/5225736
- Thread: https://ratatoskr.run/linux-security-module/2018/02/5195652/t.md

```text

>   
> +#ifdef CONFIG_PROTECTABLE_MEMORY
> +void lkdtm_WRITE_RO_PMALLOC(void)
> +{
> +	struct gen_pool *pool;
> +	int *i;
> +
> +	pool = pmalloc_create_pool("pool", 0);
> +	if (unlikely(!pool)) {
> +		pr_info("Failed preparing pool for pmalloc test.");
> +		return;
> +	}
> +
> +	i = (int *)pmalloc(pool, sizeof(int), GFP_KERNEL);
> +	if (unlikely(!i)) {
> +		pr_info("Failed allocating memory for pmalloc test.");
> +		pmalloc_destroy_pool(pool);
> +		return;
> +	}
> +
> +	*i = INT_MAX;
> +	pmalloc_protect_pool(pool);
> +
> +	pr_info("attempting bad pmalloc write at %p\n", i);
> +	*i = 0;

Seems harmless, but I don't get why *i local variable needs to be set to 0 at the end of this function.


Otherwise,

Reviewed-by: Jay Freyensee <redacted>

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