mm: fix __gup_device_huge vs unmap

BugLink: http://bugs.launchpad.net/bugs/1807469
commit a9b6de77b1a3ff729f7bfc54b2e17711776a416c upstream.

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>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/mm/gup.c b/mm/gup.c
index d2ba0be714411eb56c49ef10cc94b69276b2c789..72c921da0f3b6e050abb56dd99a0e3bc9e43d2e7 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1469,32 +1469,48 @@ 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();
@@ -1512,7 +1528,7 @@ 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);
@@ -1550,7 +1566,7 @@ 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);