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

- From: J Freyensee \<hidden\>
- Date: 2018-03-06 17:08:30 
- List: linux-mm
- Page: https://ratatoskr.run/linux-mm/2018/03/5225737
- Thread: https://ratatoskr.run/linux-security-module/2018/02/5195652/t.md

```text


On 3/6/18 9:05 AM, J Freyensee wrote:
>
>> A  +#ifdef CONFIG_PROTECTABLE_MEMORY
>> +void lkdtm_WRITE_RO_PMALLOC(void)
>> +{
>> +A A A  struct gen_pool *pool;
>> +A A A  int *i;
>> +
>> +A A A  pool = pmalloc_create_pool("pool", 0);
>> +A A A  if (unlikely(!pool)) {
>> +A A A A A A A  pr_info("Failed preparing pool for pmalloc test.");
>> +A A A A A A A  return;
>> +A A A  }
>> +
>> +A A A  i = (int *)pmalloc(pool, sizeof(int), GFP_KERNEL);
>> +A A A  if (unlikely(!i)) {
>> +A A A A A A A  pr_info("Failed allocating memory for pmalloc test.");
>> +A A A A A A A  pmalloc_destroy_pool(pool);
>> +A A A A A A A  return;
>> +A A A  }
>> +
>> +A A A  *i = INT_MAX;
>> +A A A  pmalloc_protect_pool(pool);
>> +
>> +A A A  pr_info("attempting bad pmalloc write at %p\n", i);
>> +A A A  *i = 0;
>

Opps, disregard this, this is the last series of this patch series, not the most recent one :-(.



> 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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```