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Subject: Re: Buffer Overflows
From: Jim Dennis (jimdstarshine.org)
Date: Thu Apr 27 2000 - 02:18:37 CDT

> How about it - why not implement a kernel solution to enforce memory
> boundaries so people don't have to worry about buffer overflows in their
> programming anymore (like it has been, anyway)? What does it take? How
> expensive would it be in terms of cpu performance? Is this the aim of the
> libsafe creators and the kernel group?
 
> With regards,
 
> Douglas Ostling
> Internet Entrepreneur

  Sounds like you're suggesting implement a software version of a
 "Harvard architecture" (with strict separation of code and data
 and function/return pointers stored separately from I/O and
 data buffers.

 Basically you could also redesign compilers to generate code
 that never passes data on the stack and only stores heap and
 return pointers.

 I personally think this would be a vast improvement in code
 robustness. You might still be able corrupt data with buggy
 code --- but hopefully the design would fail safe!

 (This is the worst problem with the toolchain and model ---
 the code isn't failsafe. When someone does break a bit of
 code is obviously possible to use that failure to subvert
 the process and thereby deliberately make it do very UNSAFE
 things).

 Of course I'm not a kernel designer nor am I qualified to
 write compilers. I have no idea how much this would
 break. I have no idea if it's feasible, what its performance
 characteristics would be, and whether if violates any
 standards or which necessitate a lot of rework of the
 applications (if it would be a hard porting target).

 So, though I've thought about this approach abstractly several
 times over the years, I've never pursued it very far.

 Nice of you to bring up the idea. Hasn't anyone tried it
 before. 

--
Jim Dennis                                             jdennislinuxcare.com
Linuxcare: Linux Corporate Support Team:            http://www.linuxcare.com