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

- From: J Freyensee \<hidden\>
- Date: 2018-03-06 17:08:30 
- List: linux-security-module
- Page: https://ratatoskr.run/linux-security-module/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:
>
>> ? +#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;
>

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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```