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[PATCH] mm: pte_offset_map_lock loops

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Convert those common loops using page_table_lock on the outside and
pte_offset_map within to use just pte_offset_map_lock within instead.

These all hold mmap_sem (some exclusively, some not), so at no level can a
page table be whipped away from beneath them.  But whereas pte_alloc loops
tested with the "atomic" pmd_present, these loops are testing with pmd_none,
which on i386 PAE tests both lower and upper halves.

That's now unsafe, so add a cast into pmd_none to test only the vital lower
half: we lose a little sensitivity to a corrupt middle directory, but not
enough to worry about.  It appears that i386 and UML were the only
architectures vulnerable in this way, and pgd and pud no problem.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Hugh Dickins
2005-10-29 18:16:27 -07:00
committed by Linus Torvalds
parent 8f4e2101fd
commit 705e87c0c3
7 changed files with 30 additions and 47 deletions
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17
fs/proc/task_mmu.c
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@@ -203,13 +203,14 @@ static void smaps_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
struct mem_size_stats *mss)
{
pte_t *pte, ptent;
spinlock_t *ptl;
unsigned long pfn;
struct page *page;
pte = pte_offset_map(pmd, addr);
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
do {
ptent = *pte;
if (pte_none(ptent) || !pte_present(ptent))
if (!pte_present(ptent))
continue;
mss->resident += PAGE_SIZE;
@@ -230,8 +231,8 @@ static void smaps_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
mss->private_clean += PAGE_SIZE;
}
} while (pte++, addr += PAGE_SIZE, addr != end);
pte_unmap(pte - 1);
cond_resched_lock(&vma->vm_mm->page_table_lock);
pte_unmap_unlock(pte - 1, ptl);
cond_resched();
}
static inline void smaps_pmd_range(struct vm_area_struct *vma, pud_t *pud,
@@ -285,17 +286,11 @@ static inline void smaps_pgd_range(struct vm_area_struct *vma,
static int show_smap(struct seq_file *m, void *v)
{
struct vm_area_struct *vma = v;
struct mm_struct *mm = vma->vm_mm;
struct mem_size_stats mss;
memset(&mss, 0, sizeof mss);
if (mm) {
spin_lock(&mm->page_table_lock);
if (vma->vm_mm)
smaps_pgd_range(vma, vma->vm_start, vma->vm_end, &mss);
spin_unlock(&mm->page_table_lock);
}
return show_map_internal(m, v, &mss);
}