Re: [PATCH 2/2] mm/hmm: hmm_range_fault() infinite loop

[Ralph Campbell]

On 8/27/19 11:41 AM, Jason Gunthorpe wrote:
> On Fri, Aug 23, 2019 at 03:17:53PM -0700, Ralph Campbell wrote:
>
> > Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
> >   mm/hmm.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/mm/hmm.c b/mm/hmm.c
> > index 29371485fe94..4882b83aeccb 100644
> > +++ b/mm/hmm.c
> > @@ -292,6 +292,9 @@ static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
> >   	hmm_vma_walk->last = addr;
> >   	i = (addr - range->start) >> PAGE_SHIFT;
> >   
> > +	if (write_fault && walk->vma && !(walk->vma->vm_flags & VM_WRITE))
> > +		return -EPERM;
>
> Can walk->vma be NULL here? hmm_vma_do_fault() touches it
> unconditionally.
>
> Jason
walk->vma can be NULL. hmm_vma_do_fault() no longer touches it
unconditionally, that is what the preceding patch fixes.
I suppose I could change hmm_vma_walk_hole_() to check for NULL
and fill in the pfns[] array, I just chose to handle it in
hmm_vma_do_fault().