From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 6 Jun 2014 17:30:33 +0200 From: Peter Zijlstra To: Andrey Ryabinin Cc: Andrew Morton , Linus Torvalds , linux-mm@kvack.org, linux-kernel@vger.kernel.org, koct9i@gmail.com, stable@vger.kernel.org, Hugh Dickins Subject: Re: [PATCH v2] mm: rmap: fix use-after-free in __put_anon_vma Message-ID: <20140606153033.GC11371@laptop.programming.kicks-ass.net> References: <20140606115620.GS3213@twins.programming.kicks-ass.net> <1402067370-5773-1-git-send-email-a.ryabinin@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: <1402067370-5773-1-git-send-email-a.ryabinin@samsung.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: On Fri, Jun 06, 2014 at 07:09:30PM +0400, Andrey Ryabinin wrote: > 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 patch puts freeing of child anon_vma before freeing of anon_vma->root. > > Cc: # v3.0+ Acked-by: Peter Zijlstra > Signed-off-by: Andrey Ryabinin > --- > > Changes since v1: > - just made it more simple following Peter's suggestion > > mm/rmap.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/rmap.c b/mm/rmap.c > index 9c3e773..cb5f70a 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1564,10 +1564,10 @@ 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, > -- > 1.8.5.5 >