diff options
Diffstat (limited to 'mm/rmap.c')
| -rw-r--r-- | mm/rmap.c | 42 |
1 files changed, 32 insertions, 10 deletions
diff --git a/mm/rmap.c b/mm/rmap.c index 87b9e8ad4509..92e6757f196e 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -316,7 +316,7 @@ void __init anon_vma_init(void) */ struct anon_vma *page_lock_anon_vma(struct page *page) { - struct anon_vma *anon_vma; + struct anon_vma *anon_vma, *root_anon_vma; unsigned long anon_mapping; rcu_read_lock(); @@ -327,8 +327,21 @@ struct anon_vma *page_lock_anon_vma(struct page *page) goto out; anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); - anon_vma_lock(anon_vma); - return anon_vma; + root_anon_vma = ACCESS_ONCE(anon_vma->root); + spin_lock(&root_anon_vma->lock); + + /* + * If this page is still mapped, then its anon_vma cannot have been + * freed. But if it has been unmapped, we have no security against + * the anon_vma structure being freed and reused (for another anon_vma: + * SLAB_DESTROY_BY_RCU guarantees that - so the spin_lock above cannot + * corrupt): with anon_vma_prepare() or anon_vma_fork() redirecting + * anon_vma->root before page_unlock_anon_vma() is called to unlock. + */ + if (page_mapped(page)) + return anon_vma; + + spin_unlock(&root_anon_vma->lock); out: rcu_read_unlock(); return NULL; @@ -368,7 +381,13 @@ vma_address(struct page *page, struct vm_area_struct *vma) unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) { if (PageAnon(page)) { - if (vma->anon_vma->root != page_anon_vma(page)->root) + struct anon_vma *page__anon_vma = page_anon_vma(page); + /* + * Note: swapoff's unuse_vma() is more efficient with this + * check, and needs it to match anon_vma when KSM is active. + */ + if (!vma->anon_vma || !page__anon_vma || + vma->anon_vma->root != page__anon_vma->root) return -EFAULT; } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) { if (!vma->vm_file || @@ -1551,13 +1570,14 @@ static void __hugepage_set_anon_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address, int exclusive) { struct anon_vma *anon_vma = vma->anon_vma; + BUG_ON(!anon_vma); - if (!exclusive) { - struct anon_vma_chain *avc; - avc = list_entry(vma->anon_vma_chain.prev, - struct anon_vma_chain, same_vma); - anon_vma = avc->anon_vma; - } + + if (PageAnon(page)) + return; + if (!exclusive) + anon_vma = anon_vma->root; + anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; page->mapping = (struct address_space *) anon_vma; page->index = linear_page_index(vma, address); @@ -1568,6 +1588,8 @@ void hugepage_add_anon_rmap(struct page *page, { struct anon_vma *anon_vma = vma->anon_vma; int first; + + BUG_ON(!PageLocked(page)); BUG_ON(!anon_vma); BUG_ON(address < vma->vm_start || address >= vma->vm_end); first = atomic_inc_and_test(&page->_mapcount); |