Re: [PATCH v1 1/4] mm: Fix uprobe pte be overwritten when expanding vma

[Lorenzo Stoakes]

On Fri, May 30, 2025 at 08:51:14PM +0200, David Hildenbrand wrote:
> >   	if (vp->remove) {
> > @@ -1823,6 +1829,14 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
> >   		faulted_in_anon_vma = false;
> >   	}
> > +	/*
> > +	 * If the VMA we are copying might contain a uprobe PTE, ensure
> > +	 * that we do not establish one upon merge. Otherwise, when mremap()
> > +	 * moves page tables, it will orphan the newly created PTE.
> > +	 */
> > +	if (vma->vm_file)
> > +		vmg.skip_vma_uprobe = true;
> > +
>
> Assuming we extend the VMA on the way (not merge), would we handle that
> properly?
>
> Or is that not possible on this code path or already broken either way?

I'm not sure in what context you mean expand, vma_merge_new_range() calls
vma_expand() so we call an expand a merge here, and this flag will be
obeyed.

vma_merge_new_range() -> vma_expand() -> commit_merge() -> vma_complete()
will ensure expected behaviour.

>
> --
> Cheers,
>
> David / dhildenb
>