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: <[email protected]> > Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") > Reported-by: Jan Kara <[email protected]> > Signed-off-by: Dan Williams <[email protected]>
The patch looks good to me. You can add: Reviewed-by: Jan Kara <[email protected]> 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 <[email protected]> SUSE Labs, CR _______________________________________________ Linux-nvdimm mailing list [email protected] https://lists.01.org/mailman/listinfo/linux-nvdimm
