Re: [PATCH 04/14] mm/hmm: hmm_pfns_bad() was accessing wrong struct

[John Hubbard]

On 03/16/2018 12:14 PM, jglisse@xxxxxxxxxx wrote:
> From: JÃrÃme Glisse <jglisse@xxxxxxxxxx>
> 
> The private field of mm_walk struct point to an hmm_vma_walk struct and
> not to the hmm_range struct desired. Fix to get proper struct pointer.
> 
> Signed-off-by: JÃrÃme Glisse <jglisse@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Cc: Evgeny Baskakov <ebaskakov@xxxxxxxxxx>
> Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
> Cc: Mark Hairgrove <mhairgrove@xxxxxxxxxx>
> Cc: John Hubbard <jhubbard@xxxxxxxxxx>
> ---
>  mm/hmm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 6088fa6ed137..64d9e7dae712 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -293,7 +293,8 @@ static int hmm_pfns_bad(unsigned long addr,
>  			unsigned long end,
>  			struct mm_walk *walk)
>  {
> -	struct hmm_range *range = walk->private;
> +	struct hmm_vma_walk *hmm_vma_walk = walk->private;
> +	struct hmm_range *range = hmm_vma_walk->range;
>  	hmm_pfn_t *pfns = range->pfns;
>  	unsigned long i;
>  

This fix looks good. I also checked the other uses of walk->private, of course, 
but it was only this one that was wrong.

I think this patch also belongs in -stable, because it is a simple bug fix.

For the description, well...actually, because ->range is the first element in
struct hmm_vma_walk, you probably end up with the same pointer value, both
before and after this fix. So maybe there are no symptoms to see. Maybe that's
an argument for *not* putting it in -stable, too. I'll leave that question
to more experienced people.

Either way, you can add: 

Reviewed by: John Hubbard <jhubbard@xxxxxxxxxx>

thanks,
-- 
John Hubbard
NVIDIA