Subject: Re: PT page stealing -- should we bother?
To: Chuck Cranor <chuck@xxx.research.att.com>
From: Jason R Thorpe <thorpej@zembu.com>
List: tech-kern
Date: 01/03/2001 20:29:02
On Wed, Jan 03, 2001 at 10:07:58PM -0500, Chuck Cranor wrote:
> one of the issues left in my mind is what about the remaining
> pmap_enter() calls that were not converted to PMAP_CANFAIL? would
> removing the error protection open the kernel up more to an attack by
> a malicious program (esp related to kernel memory allocation)?
> looking at the code there are plain calls in uvm_bio.c, uvm_km.c, and
> uvm_pager.c.
I can possibly see an argument for PV entries... but not for PT pages,
since kernel PT pages are always pre-allocated.
...but there's still a problem -- once you've run out of mappings to
steal, you STILL panic... so, you can "recover" for a while, but not
forever. I guess for those cases, you want the caller to decide to
return NULL or panic or whatever.
--
-- Jason R. Thorpe <thorpej@zembu.com>