[libvirt] [PATCH v2] test_driver: implement virDomainGetDiskErrors

[Michal Privoznik]

On 5/14/19 12:50 PM, Ilias Stamatis wrote:
> On Tue, May 14, 2019 at 12:40 PM John Ferlan <jferlan at redhat.com> wrote:
>>
>>
>>
>> On 5/13/19 9:04 AM, Ilias Stamatis wrote:
>>> On Mon, May 13, 2019 at 2:38 PM Michal Privoznik <mprivozn at redhat.com> wrote:
>>>>
>>>> On 5/13/19 1:26 AM, Ilias Stamatis wrote:
>>>>> Return the number of disks present in the configuration of the test
>>>>> domain when called with @errors as NULL and @maxerrors as 0.
>>>>>
>>>>> Otherwise report an error for every second disk, assigning available
>>>>> error codes in a cyclic order.
>>>>>
>>>>> Signed-off-by: Ilias Stamatis <stamatis.iliass at gmail.com>
>>>>> ---
>>>>>    src/test/test_driver.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>>>>>    1 file changed, 42 insertions(+)
>>>>>
>>>>> diff --git a/src/test/test_driver.c b/src/test/test_driver.c
>>>>> index a06d1fc402..527c2f5d3b 100644
>>>>> --- a/src/test/test_driver.c
>>>>> +++ b/src/test/test_driver.c
>>>>> @@ -3046,6 +3046,47 @@ static int testDomainSetAutostart(virDomainPtr domain,
>>>>>        return 0;
>>>>>    }
>>>>>
>>>>> +static int testDomainGetDiskErrors(virDomainPtr dom,
>>>>> +                                   virDomainDiskErrorPtr errors,
>>>>> +                                   unsigned int maxerrors,
>>>>> +                                   unsigned int flags)
>>>>> +{
>>
>> [...]
>>
>>>>> +            n++;
>>>>> +        }
>>>>> +        ret = n;
>>>>> +    }
>>>>> +
>>>>> + cleanup:
>>>>> +    virDomainObjEndAPI(&vm);
>>>>> +    if (ret < 0) {
>>>>> +        for (i = 0; i < n; i++)
>>>>> +            VIR_FREE(errors[i].disk);
>>>>> +    }
>>
>> The above got changed to :
>>
>> + cleanup:
>> +    virDomainObjEndAPI(&vm);
>> +    if (ret < 0) {
>> +        for (i = 0; i < MIN(vm->def->ndisks, maxerrors); i++)
>> +            VIR_FREE(errors[i].disk);
>> +    }
> 
> I think this change is incorrect and a bug lies in here.
> 
> If VIR_STRDUP fails above, memory for less than MIN(vm->def->ndisks,
> maxerrors) will have been allocated, and then in the cleanup code
> we'll call VIR_FREE with pointers that haven't been previously
> allocated.

That isn't a problem. User has to passed an array that we can touch. If 
they store some data in it, well, their fault - how are we supposed to 
return anything if we can't touch the array?

> 
>>
>> and Coverity got a wee bit grumpy for a couple of reasons...
>>
>>    - The virDomainObjEndAPI will set @vm = NULL which makes the MIN
>> statement quite unhappy if ret < 0
>>    - However, just moving that to after the if condition isn't good
>> enough since the testDomObjFromDomain could causes us to jump to
>> cleanup: with @vm = NULL (easily solved by return -1 there instead).

Yep, I'll be posting patch soon.

Michal