[Libguestfs] [PATCH 3/3] daemon/yara: fix undefined behavior due to Yara 4.0 API changes

[Laszlo Ersek]

On 10/12/21 17:27, Richard W.M. Jones wrote:
> On Tue, Oct 12, 2021 at 09:16:10AM -0500, Eric Blake wrote:
>> On Tue, Oct 12, 2021 at 12:36:27AM +0200, Laszlo Ersek wrote:
>>> The prototype of yara_rules_callback() is:
>>>
>>>> static int
>>>> yara_rules_callback (int code, void *message, void *data)
>>>
>>> however, in Yara commit 2b121b166d25 ("Track string matches using
>>> YR_SCAN_CONTEXT.", 2020-02-27), which was included in the upstream v4.0.0
>>> release, the rules callback prototype was changed as follows:
>>>
>>>> diff --git a/libyara/include/yara/types.h b/libyara/include/yara/types.h
>>>> index cad095cd70c2..f415033c4aa6 100644
>>>> --- a/libyara/include/yara/types.h
>>>> +++ b/libyara/include/yara/types.h
>>>> @@ -661,6 +644,7 @@ struct YR_MEMORY_BLOCK_ITERATOR
>>>>
>>>>
>>>>  typedef int (*YR_CALLBACK_FUNC)(
>>>> +    YR_SCAN_CONTEXT* context,
>>>>      int message,
>>>>      void* message_data,
>>>>      void* user_data);
>>
>> Do we intend to compile against both older and newer versions of Yara,
>> in which case we'd need a configure-time probe of which variant we
>> must compile against?  I could not quickly find documentation of a
>> minimum version of Yara that we are willing to support, at least not
>> in README or HACKING.
> 
> FWIW as Yara is a very niche feature for the digital forensics people
> I'm fine with supporting only the latest or only the most convenient
> version.  Good idea to document which version we support though.

I'd also like to clarify that I didn't ignore (part of) the feedback I
received between my posting the series and my merging it. Instead, I
simply didn't see it. I process emails in infrequent batches, in order
to improve my throughput (keep context switches as infrequent as
possible). Thus, I've not checked email between (approx.) Rich's "ACK
series" and now.

Thanks,
Laszlo