Re: [PATCH] mm: nommu: add sysctl_max_map_count() check for do_mmap()

[Hajime Tazaki]

On Mon, 06 Jul 2026 09:44:43 +0900,
Andrew Morton wrote:
> > 
> > I will follow up with another patch for the issue detected here.
> 
> Great, thanks.
> 
> > btw, I found (and sashiko also detected) several typos for this
> > particular patch.  Can I send v2 patch with the additional fix, or do
> > you prefer that I'll only send the additional patch ?
> 
> Ah.  Well.  Confession.  I actually quietly fed your changelog through
> Gemini to fix up a few things, resulting in
> 
> : The sysctl variable vm.max_map_count (sysctl_max_map_count) is not exposed
> : under !MMU configurations, but its default value (DEFAULT_MAX_MAP_COUNT)
> : is still used as a allocation limit.  Currently, this limit is enforced
> : when a VMA entry is split into two chunks (split_vma()), but it is not
> : checked during initial allocation (do_mmap()).  As a result, if a user
> : requests a large number of memory allocations, the system will continue
> : allocating until it hits an Out-Of-Memory (OOM) condition.
> : 
> : This commit introduces a check at the beginning of do_mmap() in nommu.c to
> : prevent this situation.
> : 
> : This issue was detected using the Linux Test Project (LTP) test linked
> : below.

thanks, this is perfect.

> I did this "quietly" because it feels a bit rude telling people that
> their English isn't great ;)
> 
> Lots of non-English speakers appear to be using LLMs on their
> changelogs nowadays and as long as they double-check the result, I
> think it's working very well!

thanks for handling this and a kind way to fix my mistakes.
yes, the AI era.

I will send a follow up patch for the additional issue.

-- Hajime