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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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7
mm/mempolicy.c
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@ -228,9 +228,9 @@ static int check_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
{
pte_t *orig_pte;
pte_t *pte;
spinlock_t *ptl;
spin_lock(&vma->vm_mm->page_table_lock);
orig_pte = pte = pte_offset_map(pmd, addr);
orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
do {
unsigned long pfn;
unsigned int nid;
@ -246,8 +246,7 @@ static int check_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
if (!node_isset(nid, *nodes))
break;
} while (pte++, addr += PAGE_SIZE, addr != end);
pte_unmap(orig_pte);
spin_unlock(&vma->vm_mm->page_table_lock);
pte_unmap_unlock(orig_pte, ptl);
return addr != end;
}