Messages in this thread Patch in this message | | | Date | Wed, 3 Jun 2009 16:45:52 +0200 | From | Andrea Arcangeli <> | Subject | [PATCH] ksm: fix rmap_item use after free |
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From: Andrea Arcangeli <aarcange@redhat.com>
This avoid crashing with slab debugging enabled by removing a window for memory corruption if freed slab entries are reused before we read the next pointer. Against mmotm.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> ---
diff --git a/mm/ksm.c b/mm/ksm.c index 74d921b..f060e87 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -892,7 +892,7 @@ static struct rmap_item *stable_tree_search(struct page *page, { struct rb_node *node = root_stable_tree.rb_node; struct tree_item *tree_item; - struct rmap_item *found_rmap_item; + struct rmap_item *found_rmap_item, *next_rmap_item; while (node) { int ret; @@ -907,9 +907,11 @@ static struct rmap_item *stable_tree_search(struct page *page, found_rmap_item->address == rmap_item->address)) { if (!is_zapped_item(found_rmap_item, page2)) break; + next_rmap_item = found_rmap_item->next; remove_rmap_item_from_tree(found_rmap_item); - } - found_rmap_item = found_rmap_item->next; + found_rmap_item = next_rmap_item; + } else + found_rmap_item = found_rmap_item->next; } if (!found_rmap_item) goto out_didnt_find; @@ -959,7 +961,7 @@ static int stable_tree_insert(struct page *page, while (*new) { int ret; - struct rmap_item *insert_rmap_item; + struct rmap_item *insert_rmap_item, *next_rmap_item; tree_item = rb_entry(*new, struct tree_item, node); BUG_ON(!tree_item); @@ -973,9 +975,11 @@ static int stable_tree_insert(struct page *page, insert_rmap_item->address == rmap_item->address)) { if (!is_zapped_item(insert_rmap_item, page2)) break; + next_rmap_item = insert_rmap_item->next; remove_rmap_item_from_tree(insert_rmap_item); - } - insert_rmap_item = insert_rmap_item->next; + insert_rmap_item = next_rmap_item; + } else + insert_rmap_item = insert_rmap_item->next; } if (!insert_rmap_item) return 1;
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