From 705e87c0c3c38424f7f30556c85bc20e808d2f59 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Sat, 29 Oct 2005 18:16:27 -0700 Subject: [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-) (limited to 'fs/proc') diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 7c89b454904..7e5e7ec2e36 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -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); } -- cgit v1.2.3