Re: [libvirt] [PATCH v2] test_driver: implement virDomainGetDiskErrors
On Tue, May 14, 2019 at 5:04 PM Michal Privoznik <mprivozn(a)redhat.com> wrote:
On 5/14/19 12:50 PM, Ilias Stamatis wrote:
> On Tue, May 14, 2019 at 12:40 PM John Ferlan <jferlan(a)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(a)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(a)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?
I'm not sure I understand exactly what you mean.
We can touch the array of course.
What I'm saying is that we allocate memory with VIR_STRDUP for each
errors[i].disk, but if the call fails we free this memory on our own.
However how it is implemented now we might call VIR_FREE on pointers
for which we have *not* allocated any memory.
Because in the first loop, VIR_STRDUP might fail and send us to
"cleanup". But then on cleanup we iterate over the whole errors array.
Isn't this incorrect? Do I understand something wrong?
>
>>
>> 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