From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f48.google.com (mail-wg0-f48.google.com [74.125.82.48]) by kanga.kvack.org (Postfix) with ESMTP id D63D06B0088 for ; Fri, 6 Jun 2014 11:30:36 -0400 (EDT) Received: by mail-wg0-f48.google.com with SMTP id n12so2716304wgh.31 for ; Fri, 06 Jun 2014 08:30:36 -0700 (PDT) Received: from casper.infradead.org (casper.infradead.org. [2001:770:15f::2]) by mx.google.com with ESMTPS id ys3si18144086wjc.16.2014.06.06.08.30.35 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 06 Jun 2014 08:30:35 -0700 (PDT) Date: Fri, 6 Jun 2014 17:30:33 +0200 From: Peter Zijlstra 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: quoted-printable In-Reply-To: <1402067370-5773-1-git-send-email-a.ryabinin@samsung.com> Sender: owner-linux-mm@kvack.org List-ID: 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 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->roo= t. >=20 > Cc: # v3.0+ Acked-by: Peter Zijlstra > Signed-off-by: Andrey Ryabinin > --- >=20 > Changes since v1: > - just made it more simple following Peter's suggestion >=20 > mm/rmap.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) >=20 > 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 =3D anon_vma->root; > =20 > + anon_vma_free(anon_vma); > + > if (root !=3D anon_vma && atomic_dec_and_test(&root->refcount)) > anon_vma_free(root); > - > - anon_vma_free(anon_vma); > } > =20 > static struct anon_vma *rmap_walk_anon_lock(struct page *page, > --=20 > 1.8.5.5 >=20 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org