Re: [libvirt] [PATCH v2] test_driver: implement virDomainGetDiskErrors

On 5/14/19 5:24 PM, Ilias Stamatis wrote: > On Tue, May 14, 2019 at 5:04 PM Michal Privoznik <mprivozn(a)redhat.com&gt; 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&gt; 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&gt; 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&gt; >>>>>>> --- >>>>>>> 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? Ah, now I get it. If user passes an array that is not zeroed out then we might end up passing a random pointer to free(). How about this then? if (ret < 0) { while (i > 0) VIR_FREE(errors[i--].disk); }