mm: fix __gup_device_huge vs unmap

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>

diff --git a/mm/gup.c b/mm/gup.c
index 541904a7c60fd596b1f5bc432fc7932bc005fadf..3d8472d48a0b88366e6e60e3c17fee1fe0dae7d3 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1459,32 +1459,48 @@ 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();
@@ -1502,7 +1518,7 @@ 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);
@@ -1540,7 +1556,7 @@ 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);