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| author | Hugh Dickins <hugh@veritas.com> | 2005-10-30 02:16:27 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-10-30 05:40:40 +0100 |
| commit | 705e87c0c3c38424f7f30556c85bc20e808d2f59 (patch) | |
| tree | 7a237e6266f4801385e1226cc497b47e3a2458bd /mm/mprotect.c | |
| parent | [PATCH] mm: page fault handler locking (diff) | |
| download | linux-705e87c0c3c38424f7f30556c85bc20e808d2f59.tar.xz linux-705e87c0c3c38424f7f30556c85bc20e808d2f59.zip | |
[PATCH] mm: pte_offset_map_lock loops
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>
Diffstat (limited to 'mm/mprotect.c')
| -rw-r--r-- | mm/mprotect.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c index 672a76fddd5e..17a2b52b753b 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -29,8 +29,9 @@ static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, unsigned long addr, unsigned long end, pgprot_t newprot) { pte_t *pte; + spinlock_t *ptl; - pte = pte_offset_map(pmd, addr); + pte = pte_offset_map_lock(mm, pmd, addr, &ptl); do { if (pte_present(*pte)) { pte_t ptent; @@ -44,7 +45,7 @@ static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, lazy_mmu_prot_update(ptent); } } while (pte++, addr += PAGE_SIZE, addr != end); - pte_unmap(pte - 1); + pte_unmap_unlock(pte - 1, ptl); } static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, @@ -88,7 +89,6 @@ static void change_protection(struct vm_area_struct *vma, BUG_ON(addr >= end); pgd = pgd_offset(mm, addr); flush_cache_range(vma, addr, end); - spin_lock(&mm->page_table_lock); do { next = pgd_addr_end(addr, end); if (pgd_none_or_clear_bad(pgd)) @@ -96,7 +96,6 @@ static void change_protection(struct vm_area_struct *vma, change_pud_range(mm, pgd, addr, next, newprot); } while (pgd++, addr = next, addr != end); flush_tlb_range(vma, start, end); - spin_unlock(&mm->page_table_lock); } static int |