Re: [PATCH] resolv: Fix tests by aligning hand crafted queries

[Florian Weimer <fweimer@redhat.com>]

* Adhemerval Zanella via Libc-alpha:

> On 14/06/2021 20:40, Stafford Horne via Libc-alpha wrote:
>> When testing OpenRISC I get a bus error in res_send.  This is due to the
>> buf being cast to a (HEADER *) and trying the res_send code trying to read
>> different bits of the HEADER struct including 16-bit id etc.
>> 
>> On OpenRISC reads of 16-bits and 32-bits from structures need to be 2
>> byte and 4 byte aligned, respectively.
>> 
>> To fix this we can align the hand crafted queries.
>
>
> But the res_send() interface does specify that buffer is an 'unsigned char',
> so I think the problem is in fact send_vc() (any any other code that consume
> the buffer) where the cast is in fact undefined.  I am not sure why it has
> not show any issue on architecture that trap on unaligned access, may guess
> is the stack buffer alignment is the same as the HEADER.
>
> The issue is resolv code seems to abuse this...

Right, there is a separate bug for this:

  Misaligned access in res_query.c HEADER struct
  <https://sourceware.org/bugzilla/show_bug.cgi?id=20243>

I really want to fix this, but each time I get side-tracked by other
cleanups that appear to be necessary for this. 8-(

Thanks,
Florian