early ngx_memcpy() with NGX_MEMCPY_LIMIT patch

[Vladimir Shebordaev]

2012/7/31 Maxim Dounin <mdounin at mdounin.ru>:
> Hello!
>
> On Mon, Jul 30, 2012 at 10:24:49PM +0400, Vladimir Shebordaev wrote:
>
>> Hi,
>>
>> ngx_memcpy() is invoked before ngx_cycle has been initialized, so the server
>> can segfault there when NGX_MEMCPY_LIMIT is enabled.
>>
>> diff -Naur rev4754/src/core/ngx_string.c ticket55/src/core/ngx_string.c
>> --- rev4754/src/core/ngx_string.c       2012-07-16 23:15:16.613980918 +0400
>> +++ ticket55/src/core/ngx_string.c      2012-07-23 15:41:02.863561192 +0400
>> @@ -1830,7 +1830,8 @@
>>  ngx_memcpy(void *dst, void *src, size_t n)
>>  {
>>      if (n > NGX_MEMCPY_LIMIT) {
>> -        ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, 0, "memcpy %uz bytes", n);
>> +        if (ngx_cycle)
>> +           ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, 0, "memcpy %uz bytes", n);
>>          ngx_debug_point();
>>      }
>
> This change is certainly not enough for nginx to survive too low
> NGX_MEMCPY_LIMIT set, e.g. due to the fact that ngx_debug_point()
> needs ngx_cycle as well (and actually much more than this: it
> depends on a ngx_core_module config to be available via ngx_cycle).
>
> I would rather suggest to don't try to define NGX_MEMCPY_LIMIT
> unless you understand possible implications.

Thanks, it was just helpful.

>
> Maxim Dounin
>