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From r.@seid-online.de
Subject Re: ap_log_rerror limit size
Date Wed, 13 Mar 2013 16:46:05 GMT
On Wed, Mar 13, 2013 at 04:40:50PM +0100, Hoang-Vu Dang wrote:
> I traced this into the Apache source code (ver 2.4.4). It looks like the 
> error message string is really limited by the size of 8KB.
>
> This line is in server/log.c:1097
>
> "
> static void log_error_core(const char *file, int line, int module_index,
>                            int level,
>                            apr_status_t status, const server_rec *s,
>                            const conn_rec *c,
>                            const request_rec *r, apr_pool_t *pool,
>                            const char *fmt, va_list args)
> {
>     char errstr[MAX_STRING_LEN];
> "
>
> "
> And MAX_STRING_LEN is defined in include/httpd.h:298
>
> /** The default string length */
> #define MAX_STRING_LEN HUGE_STRING_LEN
>
> /** The length of a Huge string */
> #define HUGE_STRING_LEN 8192
> "
>
> I tried to increase this value, recompile, and apparently I got a longer 
> message.
> Please correct me if I am wrong... If this is true then can anyone tell me 
> why this "HUGE_STRING_LEN" value is a hard-coded value but not a 
> configurable option ?

I can't speak for the apache core team, but such a limit usually is done
for security reasons. Tracking buffer overflows in dynamically allocated
memory can be rather tricky. Btw, what's your goal here? I get the
feeling that you try to (ab)use the error log as a place to dump large
blobs of information (traces?). Remember, this is an error log, not a
place to dump Tolstoy's War and Peace ....

 HTH Ralf Mattes

 
> Cheers, Vu
 that you try to (ab)use the error log as a place to dump large blobs of
information (traces?). Remember, this is an error log, not a
place to dump Tolstoy's War and Peace ....

 HTH Ralf Mattes
>
>
> On 03/13/2013 11:16 AM, Eric Covener wrote:
>> On Wed, Mar 13, 2013 at 6:01 AM, Hoang Vu Dang <dang.hvu@gmail.com> wrote:
>>> Hi guys,
>>>
>>> Is there any limit of the size of a message log entry? How to control 
>>> this ?
>>>
>>> I did this:
>>>
>>> ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, f->r,
>>>                  "%s", buffer);
>>>
>>> And the buffer was truncated on the error log. I check the strlen of the 
>>> buffer and it was about 320K, and I got only around: ~ 8KB
>> If it's more than PIPE_BUF, it won't be atomic and can be interleaved
>> with other entries.  Are you sure it's truncated and not just spread
>> out?

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