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@xxxxxxxxxxxxxxx>
> Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings")
> Reported-by: Jan Kara <jack@xxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
The patch looks good to me. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
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@xxxxxxxx>
SUSE Labs, CR
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