Re: [RFC PATCH 00/18] Try to free user PTE page table pages

[Qi Zheng]

On 2022/5/18 10:56 PM, Matthew Wilcox wrote:
> On Wed, May 18, 2022 at 04:51:06PM +0200, David Hildenbrand wrote:
> > yes, I talked about the involved challenges, especially, how malicious
> > user space can trigger allocation of almost elusively page tables and
> > essentially consume a lot of unmovable+unswappable memory and even store
> > secrets in the page table structure.
>
> There are a lot of ways for userspace to consume a large amount of
> kernel memory.  For example, one can open a file and set file locks on

Yes, malicious programs are really hard to avoid, maybe we should try to
solve some common cases first (such as empty PTE tables).

> alternate bytes.  We generally handle this by accounting the memory to
> the process and let the OOM killer, rlimits, memcg or other mechanism
> take care of it.  Just because page tables are (generally) reclaimable
> doesn't mean we need to treat them specially.

--
Thanks,
Qi