Re: [Qemu-devel] [PATCH v2 6/7] libcacard/vcard_emul_nss: Assert vreaderOpt isn't null

[Markus Armbruster]

Michael Tokarev <address@hidden> writes:

> 23.05.2014 22:16, Michael Tokarev пишет:
>> 23.05.2014 22:09, Michael Tokarev wrote:
>>> 23.05.2014 15:24, Markus Armbruster wrote:
>>>> It's not locally obvious, and Coverity can't see it either.
>>>>
>>>> Signed-off-by: Markus Armbruster <address@hidden>
>>>> Reviewed-by: Alon Levy <address@hidden>
>>>> ---
>>>>  libcacard/vcard_emul_nss.c | 1 +
>>>>  1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/libcacard/vcard_emul_nss.c b/libcacard/vcard_emul_nss.c
>>>> index 2048917..4f55e44 100644
>>>> --- a/libcacard/vcard_emul_nss.c
>>>> +++ b/libcacard/vcard_emul_nss.c
>>>> @@ -1181,6 +1181,7 @@ vcard_emul_options(const char *args)
>>>>                  vreaderOpt = g_renew(VirtualReaderOptions, opts->vreader,
>>>>                                       reader_count);
>>>>              }
>>>> +            assert(vreaderOpt);
>>>>              opts->vreader = vreaderOpt;
>>>>              vreaderOpt = &vreaderOpt[opts->vreader_count];
>>>>              vreaderOpt->name = g_strndup(name, name_length);
>>>
>>> Shouldn't the assignment be moved up one line into the if {}
>>> statement instead?
>> 
>> Actually it looks like this code is just buggy, it works for just
>> one iteration.  Because at this place, vreaderOpts will be non-NULL
>> only if we expanded the array.  If we didn't (we do that in
>> READER_STEP increments), we'll be assigning NULL to opts->vreader,
>> because vreaderOpt will _really_ be NULL here.

You're right.  When I saw the conditional realloc, I jumped to convince
myself that it's always executed in the first loop iteration, but missed
the fact that vreaderOpt is reset to null on *every* iteration.

> So, the real fix is:
>
> 1) drop = NULL at declaration of vreaderOpt;
> 2) do not mention vreaderOpt inside the if{} statement at
>    all, we don't need indirection there;
> 3) drop this opts->vreader assignment
>
> and ofcourse do not add the assert as in the patch above ;)

I'll review it.  Thanks!