Miloslav Trmac found a heap overflow in the way texindex handles data from
certain index files.

The texindex utility contains a heap overflow; when the data for a
generated index is larger than 500,000 bytes, an incorrect reallocation
code in readline() allows heap overflow by index lines longer than 400
bytes.


It looks like the code in readline() of texindex.c has some crazy arithmetic.

 char *buffer = linebuffer->buffer;
 char *p = linebuffer->buffer;
 char *end = p + linebuffer->size;

 while (1)
 {
  int c = getc (stream);
  if (p == end)
  {
   buffer = (char *) xrealloc (buffer, linebuffer->size *= 2);
   p += buffer - linebuffer->buffer;
   end += buffer - linebuffer->buffer;
   linebuffer->buffer = buffer;

It would seem that when p == end, p and end are assigned what could be a random
memory addresses as the location of buffer is likely to change with a realloc
from a size of 200 to 400 bytes. p then proceedes to dump trash on the heap
until the current line ends.