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From: Jan Kara <jack@suse.cz>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Jan Kara <jack@suse.cz>,
	linux-nvdimm@lists.01.org, david@fromorbit.com,
	stable@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, hch@lst.de
Subject: Re: [PATCH v9 5/9] mm: fix __gup_device_huge vs unmap
Date: Wed, 9 May 2018 12:46:35 +0200	[thread overview]
Message-ID: <20180509104635.57upe2fri7abqu7p@quack2.suse.cz> (raw)
In-Reply-To: <152461280975.17530.2817946409563456285.stgit@dwillia2-desk3.amr.corp.intel.com>

On Tue 24-04-18 16:33:29, Dan Williams wrote:
> get_user_pages_fast() for device pages is missing the typical validation
> that all page references have been taken while the mapping was valid.
> Without this validation truncate operations can not reliably coordinate
> against new page reference events like O_DIRECT.
> 
> Cc: <stable@vger.kernel.org>
> Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings")
> Reported-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

The patch looks good to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza


> ---
>  mm/gup.c |   36 ++++++++++++++++++++++++++----------
>  1 file changed, 26 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index 76af4cfeaf68..84dd2063ca3d 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1456,32 +1456,48 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
>  	return 1;
>  }
>  
> -static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
> +static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
>  		unsigned long end, struct page **pages, int *nr)
>  {
>  	unsigned long fault_pfn;
> +	int nr_start = *nr;
> +
> +	fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
> +	if (!__gup_device_huge(fault_pfn, addr, end, pages, nr))
> +		return 0;
>  
> -	fault_pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
> -	return __gup_device_huge(fault_pfn, addr, end, pages, nr);
> +	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
> +		undo_dev_pagemap(nr, nr_start, pages);
> +		return 0;
> +	}
> +	return 1;
>  }
>  
> -static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
> +static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
>  		unsigned long end, struct page **pages, int *nr)
>  {
>  	unsigned long fault_pfn;
> +	int nr_start = *nr;
> +
> +	fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
> +	if (!__gup_device_huge(fault_pfn, addr, end, pages, nr))
> +		return 0;
>  
> -	fault_pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
> -	return __gup_device_huge(fault_pfn, addr, end, pages, nr);
> +	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
> +		undo_dev_pagemap(nr, nr_start, pages);
> +		return 0;
> +	}
> +	return 1;
>  }
>  #else
> -static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
> +static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
>  		unsigned long end, struct page **pages, int *nr)
>  {
>  	BUILD_BUG();
>  	return 0;
>  }
>  
> -static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
> +static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
>  		unsigned long end, struct page **pages, int *nr)
>  {
>  	BUILD_BUG();
> @@ -1499,7 +1515,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
>  		return 0;
>  
>  	if (pmd_devmap(orig))
> -		return __gup_device_huge_pmd(orig, addr, end, pages, nr);
> +		return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr);
>  
>  	refs = 0;
>  	page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
> @@ -1537,7 +1553,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
>  		return 0;
>  
>  	if (pud_devmap(orig))
> -		return __gup_device_huge_pud(orig, addr, end, pages, nr);
> +		return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr);
>  
>  	refs = 0;
>  	page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR
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  reply	other threads:[~2018-05-09 10:46 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-24 23:33 [PATCH v9 0/9] dax: fix dma vs truncate/hole-punch Dan Williams
2018-04-24 23:33 ` [PATCH v9 1/9] dax, dm: introduce ->fs_{claim, release}() dax_device infrastructure Dan Williams
2018-05-09 10:37   ` Jan Kara
2018-04-24 23:33 ` [PATCH v9 2/9] mm, dax: enable filesystems to trigger dev_pagemap ->page_free callbacks Dan Williams
2018-05-16  7:20   ` Dan Williams
2018-04-24 23:33 ` [PATCH v9 3/9] memremap: split devm_memremap_pages() and memremap() infrastructure Dan Williams
2018-05-09 10:29   ` Jan Kara
2018-04-24 23:33 ` [PATCH v9 4/9] mm, dev_pagemap: introduce CONFIG_DEV_PAGEMAP_OPS Dan Williams
2018-04-24 23:33 ` [PATCH v9 5/9] mm: fix __gup_device_huge vs unmap Dan Williams
2018-05-09 10:46   ` Jan Kara [this message]
2018-04-24 23:33 ` [PATCH v9 6/9] mm, fs, dax: handle layout changes to pinned dax mappings Dan Williams
2018-05-09 10:56   ` Jan Kara
2018-05-09 22:06     ` Dan Williams
2018-04-24 23:33 ` [PATCH v9 7/9] xfs: prepare xfs_break_layouts() to be called with XFS_MMAPLOCK_EXCL Dan Williams
2018-04-24 23:33 ` [PATCH v9 8/9] xfs: prepare xfs_break_layouts() for another layout type Dan Williams
2018-04-24 23:33 ` [PATCH v9 9/9] xfs, dax: introduce xfs_break_dax_layouts() Dan Williams
2018-05-09 12:27   ` Jan Kara
2018-05-09 22:54     ` Dan Williams
2018-05-09 14:38   ` Darrick J. Wong
2018-05-03 23:53 ` [PATCH v9 0/9] dax: fix dma vs truncate/hole-punch Dan Williams
2018-05-08  0:16   ` Darrick J. Wong

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