Re: [PATCH v2 00/15] Avoid MAP_FIXED gap exposure

[Andrew Morton]

On Tue, 25 Jun 2024 15:11:30 -0400 "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> wrote:

> It is now possible to walk the vma tree using the rcu read locks and is
> beneficial to do so to reduce lock contention.  Doing so while a
> MAP_FIXED mapping is executing means that a reader may see a gap in the
> vma tree that should never logically exist - and does not when using the
> mmap lock in read mode.  The temporal gap exists because mmap_region()
> calls munmap() prior to installing the new mapping.

What are the consequences when this race hits?  IOW, why do we need to
change anything?