Re: [Qemu-devel] [PATCH] crypto: afalg: fix a NULL pointer dereference

["Longpeng (Mike)" <longpeng2@huawei.com>]

On 2017/11/7 17:16, Daniel P. Berrange wrote:

> On Tue, Nov 07, 2017 at 10:27:10AM +0800, Longpeng (Mike) wrote:
>>
>>
>> On 2017/11/7 1:00, Eric Blake wrote:
>>
>>> On 11/06/2017 12:21 AM, Longpeng(Mike) wrote:
>>>> Test-crypto-hash calls qcrypto_hash_bytesv/digest/base64 with
>>>> errp=NULL, this will cause a NULL poniter deference if afalg_driver
>>>
>>> s/poniter deference/pointer dereference/
>>>
>>
>> OK.
>>
>>>> doesn't support requested algos:
>>>>     ret = qcrypto_hash_afalg_driver.hash_bytesv(alg, iov, niov,
>>>>                                                 result, resultlen,
>>>>                                                 errp);
>>>>     if (ret == 0) {
>>>>         return ret;
>>>>     }
>>>>
>>>>     error_free(*errp);  // <--- here
>>>>
>>>> So we must check 'errp & *errp' before dereference.
>>>
>>> No, if we are going to blindly ignore the error from the hash_bytesv()
>>> call, then we should pass NULL rather than errp.
>>>
>>
>> The 'errp' in this palce is convenient for debug, it can tell us the reason for
>> failure without stepping into afalg_driver's hash_bytesv().
> 
> It doesn't do anything useful for debug, because we are just immediately
> throwing away the error without printing it anywhere. Just pass NULL into
> the hash_bytesv call above.
> 

OK..

Afalg-backend cipher/hmac has the same usage, so maybe I need to correct all of
them.

> Regards,
> Daniel


-- 
Regards,
Longpeng(Mike)