Re: [PATCH 4/5] mm: gup: fix potential pgmap refcnt leak in __gup_device_huge()

[John Hubbard]

On 8/7/21 11:45 AM, Andrew Morton wrote:
> On Sat, 7 Aug 2021 11:41:12 -0700 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> > We can simplify further, and remove the troublesome multiple return points?
>
> oops.

I sent a reviewed by to the "+" fixup email, but just realized that that did not
hit the main
 mailing list. So:



For the end result of these stacked fixes to this file:



Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>



thanks,

--

John Hubbard

NVIDIA
> --- a/mm/gup.c~mm-gup-fix-potential-pgmap-refcnt-leak-in-__gup_device_huge-fix-fix
> +++ a/mm/gup.c
> @@ -2240,6 +2240,7 @@ static int __gup_device_huge(unsigned lo
>   {
>   	int nr_start = *nr;
>   	struct dev_pagemap *pgmap = NULL;
> +	int ret = 1;
>   
>   	do {
>   		struct page *page = pfn_to_page(pfn);
> @@ -2247,12 +2248,14 @@ static int __gup_device_huge(unsigned lo
>   		pgmap = get_dev_pagemap(pfn, pgmap);
>   		if (unlikely(!pgmap)) {
>   			undo_dev_pagemap(nr, nr_start, flags, pages);
> +			ret = 0;
>   			break;
>   		}
>   		SetPageReferenced(page);
>   		pages[*nr] = page;
>   		if (unlikely(!try_grab_page(page, flags))) {
>   			undo_dev_pagemap(nr, nr_start, flags, pages);
> +			ret = 0;
>   			break;
>   		}
>   		(*nr)++;
> @@ -2260,7 +2263,7 @@ static int __gup_device_huge(unsigned lo
>   	} while (addr += PAGE_SIZE, addr != end);
>   
>   	put_dev_pagemap(pgmap);
> -	return 1;
> +	return ret;
>   }
>   
>   static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
>
> Not sure if it's worth bothering, really...