[mythtv] Teletxt buffer overrun (was: text from mythfrontend (teletext related))

Erik Arendse erik_nospam.arendse at bigfoot.com
Mon Jul 28 09:55:09 EDT 2003


At 27-7-2003 22:11, Martin Moeller wrote:
>ÐÐ
>- And WHAT was it?
>- Absolutely no idea.
>text buffer overflow
>text buffer overflow
>text buffer overflow
>pagenr : 8870000, vbipagenr : 8880000

What you see above is the buffer to write the text to disk complaining it 
can't keep up. This can be fixed with some tuning of buffersizes etc. It is 
not important or dangerous however, just means you have lost a page of 
subtitles.

What Isaac is complaining about is char-buffer overrun in the C-code. This 
is _very_bad_ coding, and I am responsible :-)

When writing the text to the text-buffer (which is later written to disk in 
the write-thread) I just copied to text without checking lengths. This is 
bad form, and was only intended as first version beta-code. Unfortunately I 
stopped using and coding mythTV just afterwards, so now it is you 
problem... Just find out where the text is copies to the frames and add all 
normal sanity checks. The problem manifests on noisy transmissions where 
the VBI parser (from AleVT) can spill out garbage with illegal lengths, 
this must be detected and discarded in the mythTV code.

If you can't locate it by looking at the source you should use Valgrind on 
anything like that on the project and you will find the offending code in 
no time.

Erik




More information about the mythtv-dev mailing list