diff options
| -rw-r--r-- | mm/memory.c | 63 | ||||
| -rw-r--r-- | mm/rmap.c | 7 |
2 files changed, 46 insertions, 24 deletions
diff --git a/mm/memory.c b/mm/memory.c index 107b619cfb16..3666a4c6dd22 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -350,6 +350,22 @@ void print_bad_pte(struct vm_area_struct *vma, pte_t pte, unsigned long vaddr) } /* + * page_is_anon applies strict checks for an anonymous page belonging to + * this vma at this address. It is used on VM_UNPAGED vmas, which are + * usually populated with shared originals (which must not be counted), + * but occasionally contain private COWed copies (when !VM_SHARED, or + * perhaps via ptrace when VM_SHARED). An mmap of /dev/mem might window + * free pages, pages from other processes, or from other parts of this: + * it's tricky, but try not to be deceived by foreign anonymous pages. + */ +static inline int page_is_anon(struct page *page, + struct vm_area_struct *vma, unsigned long addr) +{ + return page && PageAnon(page) && page_mapped(page) && + page_address_in_vma(page, vma) == addr; +} + +/* * copy one vm_area from one task to the other. Assumes the page tables * already present in the new task to be cleared in the whole range * covered by this vma. @@ -381,23 +397,22 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, goto out_set_pte; } - /* If the region is VM_UNPAGED, the mapping is not - * mapped via rmap - duplicate the pte as is. - */ - if (vm_flags & VM_UNPAGED) - goto out_set_pte; - pfn = pte_pfn(pte); - /* If the pte points outside of valid memory but + page = pfn_valid(pfn)? pfn_to_page(pfn): NULL; + + if (unlikely(vm_flags & VM_UNPAGED)) + if (!page_is_anon(page, vma, addr)) + goto out_set_pte; + + /* + * If the pte points outside of valid memory but * the region is not VM_UNPAGED, we have a problem. */ - if (unlikely(!pfn_valid(pfn))) { + if (unlikely(!page)) { print_bad_pte(vma, pte, addr); goto out_set_pte; /* try to do something sane */ } - page = pfn_to_page(pfn); - /* * If it's a COW mapping, write protect it both * in the parent and the child @@ -568,17 +583,20 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, continue; } if (pte_present(ptent)) { - struct page *page = NULL; + struct page *page; + unsigned long pfn; (*zap_work) -= PAGE_SIZE; - if (!(vma->vm_flags & VM_UNPAGED)) { - unsigned long pfn = pte_pfn(ptent); - if (unlikely(!pfn_valid(pfn))) - print_bad_pte(vma, ptent, addr); - else - page = pfn_to_page(pfn); - } + pfn = pte_pfn(ptent); + page = pfn_valid(pfn)? pfn_to_page(pfn): NULL; + + if (unlikely(vma->vm_flags & VM_UNPAGED)) { + if (!page_is_anon(page, vma, addr)) + page = NULL; + } else if (unlikely(!page)) + print_bad_pte(vma, ptent, addr); + if (unlikely(details) && page) { /* * unmap_shared_mapping_pages() wants to @@ -1295,10 +1313,11 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, old_page = pfn_to_page(pfn); src_page = old_page; - if (unlikely(vma->vm_flags & VM_UNPAGED)) { - old_page = NULL; - goto gotten; - } + if (unlikely(vma->vm_flags & VM_UNPAGED)) + if (!page_is_anon(old_page, vma, address)) { + old_page = NULL; + goto gotten; + } if (PageAnon(old_page) && !TestSetPageLocked(old_page)) { int reuse = can_share_swap_page(old_page); diff --git a/mm/rmap.c b/mm/rmap.c index 377d417ec15f..2e034a0b89ab 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -225,7 +225,9 @@ vma_address(struct page *page, struct vm_area_struct *vma) /* * At what user virtual address is page expected in vma? checking that the - * page matches the vma: currently only used by unuse_process, on anon pages. + * page matches the vma: currently only used on anon pages, by unuse_vma; + * and by extraordinary checks on anon pages in VM_UNPAGED vmas, taking + * care that an mmap of /dev/mem might window free and foreign pages. */ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) { @@ -234,7 +236,8 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) (void *)page->mapping - PAGE_MAPPING_ANON) return -EFAULT; } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) { - if (vma->vm_file->f_mapping != page->mapping) + if (!vma->vm_file || + vma->vm_file->f_mapping != page->mapping) return -EFAULT; } else return -EFAULT; |