Re: OS stopping stack buffer overflow exploits

From: Rogier Wolff (
Date: Sun Jun 04 2000 - 00:41:25 EST

Robert Redelmeier wrote:
> 2) On syscall entry, the kernel could check the page tables
> to be sure that the return address is from code pages (read-only),
> and not from data pages (read-write). The kernel would log and
> terminate any such process. Kill some nasty bugs this way too.
> This assumes an exploit can do limited damage without syscalls.

I've always be arguing that blocking the "exec /bin/sh" (that standard
exploits do) doesn't help. You can implement a shell like thingy
inside the exploit.

So your suggestion would also help against this attack.

Until I realized that instead of doing the "int 80" to call the
kernel, the exploit will just have to do "call <syscall entry point in

In short you'll make a change that is simply incompatible with the
current exploits, but they will be "compatible" again in a few weeks,
well before everyone has upgraded to the new kernel.


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