mm: softdirty: unmapped addresses between VMAs are clean
commit 81d0fa623c
upstream.
If a /proc/pid/pagemap read spans a [VMA, an unmapped region, then a
VM_SOFTDIRTY VMA], the virtual pages in the unmapped region are reported
as softdirty. Here's a program to demonstrate the bug:
int main() {
const uint64_t PAGEMAP_SOFTDIRTY = 1ul << 55;
uint64_t pme[3];
int fd = open("/proc/self/pagemap", O_RDONLY);;
char *m = mmap(NULL, 3 * getpagesize(), PROT_READ,
MAP_ANONYMOUS | MAP_SHARED, -1, 0);
munmap(m + getpagesize(), getpagesize());
pread(fd, pme, 24, (unsigned long) m / getpagesize() * 8);
assert(pme[0] & PAGEMAP_SOFTDIRTY); /* passes */
assert(!(pme[1] & PAGEMAP_SOFTDIRTY)); /* fails */
assert(pme[2] & PAGEMAP_SOFTDIRTY); /* passes */
return 0;
}
(Note that all pages in new VMAs are softdirty until cleared).
Tested:
Used the program given above. I'm going to include this code in
a selftest in the future.
[n-horiguchi@ah.jp.nec.com: prevent pagemap_pte_range() from overrunning]
Signed-off-by: Peter Feiner <pfeiner@google.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Jamie Liu <jamieliu@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
1127e68e4b
commit
620d77bda9
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@ -995,7 +995,6 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
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spinlock_t *ptl;
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pte_t *pte;
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int err = 0;
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pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2));
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/* find the first VMA at or above 'addr' */
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vma = find_vma(walk->mm, addr);
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@ -1009,6 +1008,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
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for (; addr != end; addr += PAGE_SIZE) {
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unsigned long offset;
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pagemap_entry_t pme;
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offset = (addr & ~PAGEMAP_WALK_MASK) >>
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PAGE_SHIFT;
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@ -1023,32 +1023,51 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
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if (pmd_trans_unstable(pmd))
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return 0;
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for (; addr != end; addr += PAGE_SIZE) {
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int flags2;
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/* check to see if we've left 'vma' behind
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* and need a new, higher one */
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if (vma && (addr >= vma->vm_end)) {
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vma = find_vma(walk->mm, addr);
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if (vma && (vma->vm_flags & VM_SOFTDIRTY))
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flags2 = __PM_SOFT_DIRTY;
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else
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flags2 = 0;
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pme = make_pme(PM_NOT_PRESENT(pm->v2) | PM_STATUS2(pm->v2, flags2));
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while (1) {
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/* End of address space hole, which we mark as non-present. */
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unsigned long hole_end;
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if (vma)
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hole_end = min(end, vma->vm_start);
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else
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hole_end = end;
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for (; addr < hole_end; addr += PAGE_SIZE) {
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pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2));
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err = add_to_pagemap(addr, &pme, pm);
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if (err)
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return err;
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}
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/* check that 'vma' actually covers this address,
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* and that it isn't a huge page vma */
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if (vma && (vma->vm_start <= addr) &&
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!is_vm_hugetlb_page(vma)) {
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if (!vma || vma->vm_start >= end)
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break;
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/*
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* We can't possibly be in a hugetlb VMA. In general,
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* for a mm_walk with a pmd_entry and a hugetlb_entry,
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* the pmd_entry can only be called on addresses in a
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* hugetlb if the walk starts in a non-hugetlb VMA and
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* spans a hugepage VMA. Since pagemap_read walks are
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* PMD-sized and PMD-aligned, this will never be true.
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*/
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BUG_ON(is_vm_hugetlb_page(vma));
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/* Addresses in the VMA. */
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for (; addr < min(end, vma->vm_end); addr += PAGE_SIZE) {
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pagemap_entry_t pme;
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pte = pte_offset_map(pmd, addr);
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pte_to_pagemap_entry(&pme, pm, vma, addr, *pte);
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/* unmap before userspace copy */
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pte_unmap(pte);
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err = add_to_pagemap(addr, &pme, pm);
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if (err)
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return err;
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}
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err = add_to_pagemap(addr, &pme, pm);
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if (err)
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return err;
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if (addr == end)
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break;
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vma = find_vma(walk->mm, addr);
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}
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cond_resched();
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