# Re: \[PATCH 2/5\] crypto: hisilicon/sec - add ahash alg features for Kunpeng920

- From: yekai(A) \<hidden\>
- Date: 2021-08-28 03:16:52 
- List: linux-crypto
- Page: https://ratatoskr.run/linux-crypto/2021/08/8490951
- Thread: https://ratatoskr.run/linux-crypto/2021/08/8490951/t.md

```text


On 2021/8/27 16:36, Herbert Xu wrote:
> On Sat, Aug 21, 2021 at 05:07:00PM +0800, yekai(A) wrote:
>>
>>
>> On 2021/8/21 15:25, Herbert Xu wrote:
>>> On Fri, Aug 13, 2021 at 05:40:23PM +0800, Kai Ye wrote:
>>>>
>>>> +static int sec_ahash_import(struct ahash_request *req, const void *in)
>>>> +{
>>>> +	/*
>>>> +	 * Import partial state of the transformation. This function loads the
>>>> +	 * entire state of the ongoing transformation from a provided block of
>>>> +	 * data so the transformation can continue from this point onward.
>>>> +	 */
>>>> +	struct sec_req *sreq = ahash_request_ctx(req);
>>>> +
>>>> +	memcpy(sreq, in, sizeof(struct sec_req));
>>>> +	return 0;
>>>> +}
>>>
>>> Please explain how this works given that you've got pointers in
>>> struct sec_req?
>>>
>>> Thanks,
>>>
>> We have set the sec_req size by use the "crypto_ahash_set_reqsize" in ahash
>> tfm init process. The crypto will allocate memory for the sec_req by
>> "__ctx[]". And we can got the pointers by use ahash_request. like
>>
>> void *temp = ahash_request_ctx(req);
>> struct sec_req *sreq = (struct sec_req)temp;
>>
>> The value of halg.statesize is sizeof(struct sec_req), so the user can get
>> the statesize.
>
> The data you get from the import could be random garbage.  Please
> explain how you avoid dereferencing random pointers in your code
> through the import path.
>
> Thanks,
>

I refered to other people's plans. Modify the value of halg.statesize
is sizeof(struct sec_req) + sizeof(u32), So user can allocate an extra sizeof(u32) memory. The driver will write a tag number to the addr in the export process, then the driver will check the pointers by the tag number through the import path.
I think this plan can avoid random pointers.

Thanks
Kai
```