Re: [RFC] prevention of syscalls from writable segments, breaking bug exploits

[Andi Kleen]

On Wed, Jan 03, 2001 at 04:54:38PM -0500, Alexander Viro wrote:
> 
> Win: 0
> Loss: cost of find_vma() (and down(&mm->mmap_sem), BTW) on every system

It could actually be optimized a lot, e.g. by just read/writing to a byte
in the caller's current code page and handling the exception. 

But I agree with you that it's rather useless. It'll break some existing 
exploits, but it's so easy to workaround that exploit writers would quickly
adapt and then you have a ugly check with no purpose after a few weeks.

-Andi
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