Re: [PATCH v4 5/6] mm: always lock new vma before inserting into vma tree

[Andrew Morton]

On Mon, 14 Aug 2023 16:54:01 +0200 Jann Horn <jannh@xxxxxxxxxx> wrote:

> > @@ -403,6 +403,8 @@ static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma)
> >
> >   vma_iter_store(&vmi, vma);
> >
> > + vma_start_write(vma);
> > +
> >   if (vma->vm_file) {
> >  mapping = vma->vm_file->f_mapping;
> >  i_mmap_lock_write(mapping);
> 
> The "vma_start_write()" has to be ordered before the
> "vma_iter_store(&vmi, vma)".

Thanks.  This?


--- a/mm/mmap.c~mm-always-lock-new-vma-before-inserting-into-vma-tree-fix
+++ a/mm/mmap.c
@@ -401,10 +401,10 @@ static int vma_link(struct mm_struct *mm
 	if (vma_iter_prealloc(&vmi, vma))
 		return -ENOMEM;
 
-	vma_iter_store(&vmi, vma);
-
 	vma_start_write(vma);
 
+	vma_iter_store(&vmi, vma);
+
 	if (vma->vm_file) {
 		mapping = vma->vm_file->f_mapping;
 		i_mmap_lock_write(mapping);
_