Buffer overflow and code execution on iSeries

On the Midrange-L list someone made the following comment about BIND and buffer 
overrun.
 
>remote execution via buffer overflow doesn't seem likely or possible on an 
>iSeries box. 
 
Now, that got me thinking, and maybe I just need to go read Leif's book again, 
but... 
 
Program A has it's storage space, and let's say there's a field called 'FLD1' 
in that space, now, as we all know, when I call program B and pass it FLD1 as a 
parm, only the address goes over, so if FLD1 is 30 bytes in program A, but it's 
60 bytes in program B I can overwrite whatever is in memory after FLD1 in 
program A. Now, that _might_ be FLD2, right? 
 
What if FLD2 is the pointer to program C. Could program B change the value in 
FLD2 such that on the next attempted call to program C I actually called 
something else? Is this where I'd get caught by the tagged-pointer validation? 
But couldn't I load the appropriate values into the memory to make a valid 
pointer, I know you can create one per-Leif's book. 
 
So, as I'm thinking about it, code execution via buffer overrun is unlikely, 
ne, VERY unlikely, on iSeries, but it _is_ possible. Right?
 
-Walden
 
------------
Walden H Leverich III
Tech Software
(516) 627-3800 x11
WaldenL@xxxxxxxxxxxxxxx
http://www.TechSoftInc.com <blocked::http://www.techsoftinc.com/> 

Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)