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

[Jason Gunthorpe]

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