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Subject: Re: [PATCH 4/5] mm: gup: fix potential pgmap refcnt leak in
 __gup_device_huge()
To:     Andrew Morton <akpm@linux-foundation.org>,
        Miaohe Lin <linmiaohe@huawei.com>, <imbrenda@linux.ibm.com>,
        <kirill.shutemov@linux.intel.com>, <jack@suse.cz>,
        <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>
References: <20210807093620.21347-1-linmiaohe@huawei.com>
 <20210807093620.21347-5-linmiaohe@huawei.com>
 <20210807114112.6e45b31c65dd62169fee8718@linux-foundation.org>
 <20210807114545.eaee318909a9215c4e056aa3@linux-foundation.org>
From:   John Hubbard <jhubbard@nvidia.com>
Message-ID: <87f2ff42-9d96-3ecb-dada-d347a3fa95e6@nvidia.com>
Date:   Sun, 8 Aug 2021 14:16:53 -0700
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On 8/7/21 11:45 AM, Andrew Morton wrote:
> On Sat, 7 Aug 2021 11:41:12 -0700 Andrew Morton <akpm@linux-foundation.org> 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@nvidia.com>


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...
>