From 624483f3ea82598ab0f62f1bdb9177f531ab1892 Mon Sep 17 00:00:00 2001 From: Andrey Ryabinin Date: Fri, 6 Jun 2014 19:09:30 +0400 Subject: [PATCH] mm: rmap: fix use-after-free in __put_anon_vma While working address sanitizer for kernel I've discovered use-after-free bug in __put_anon_vma. For the last anon_vma, anon_vma->root freed before child anon_vma. Later in anon_vma_free(anon_vma) we are referencing to already freed anon_vma->root to check rwsem. This fixes it by freeing the child anon_vma before freeing anon_vma->root. Signed-off-by: Andrey Ryabinin Acked-by: Peter Zijlstra Cc: # v3.0+ Signed-off-by: Linus Torvalds --- mm/rmap.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 9c3e773..83bfafa 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1564,10 +1564,9 @@ void __put_anon_vma(struct anon_vma *anon_vma) { struct anon_vma *root = anon_vma->root; + anon_vma_free(anon_vma); if (root != anon_vma && atomic_dec_and_test(&root->refcount)) anon_vma_free(root); - - anon_vma_free(anon_vma); } static struct anon_vma *rmap_walk_anon_lock(struct page *page, -- 1.9.1