[PATCH v3, resend] Fix misaligned accesses to fields in HEADER struct defined in <arpa/nameser_compat.h>

[John David Anglin]

On 2022-03-16 12:15 p.m., Andreas Schwab wrote:
> On Mär 15 2022, John David Anglin wrote:
>
>> diff --git a/resolv/res_mkquery.c b/resolv/res_mkquery.c
>> index 5bc5b41531..9b82c82157 100644
>> --- a/resolv/res_mkquery.c
>> +++ b/resolv/res_mkquery.c
>> @@ -193,6 +193,15 @@ context_mkquery_common (struct resolv_context *ctx,
>>     return result;
>>   }
>>   
>> +/* The structure HEADER is normally aligned to a word boundary and its
>> +   fields are accessed using word loads and stores.  We need to access
>> +   this structure when it is aligned on a byte boundary.  This can cause
>> +   problems on machines with strict alignment.  So, we create a new
>> +   typedef to reduce its alignment to one.  This ensures the fields are
>> +   accessed with byte loads and stores.  */
>> +typedef HEADER __attribute__ ((__aligned__(1))) UHEADER;
>> +#define HEADER UHEADER
>> +
> The only use of HEADER below that point is in __res_nopt, and AFACS the
> only caller __res_context_query always uses aligned memory.
Yes, it appears the callers of __res_nopt always use aligned memory.  I'll check if this hunk can
be removed.

-- 
John David Anglin  dave.anglin@bell.net