From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f200.google.com (mail-io0-f200.google.com [209.85.223.200]) by kanga.kvack.org (Postfix) with ESMTP id 43A1D6B0253 for ; Mon, 1 Aug 2016 10:54:14 -0400 (EDT) Received: by mail-io0-f200.google.com with SMTP id n69so309738651ion.0 for ; Mon, 01 Aug 2016 07:54:14 -0700 (PDT) Received: from EUR01-HE1-obe.outbound.protection.outlook.com (mail-he1eur01on0098.outbound.protection.outlook.com. [104.47.0.98]) by mx.google.com with ESMTPS id v73si19883329oia.111.2016.08.01.07.54.08 for (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 01 Aug 2016 07:54:09 -0700 (PDT) Subject: Re: [PATCH v8 2/3] mm, kasan: align free_meta_offset on sizeof(void*) References: <1469719879-11761-1-git-send-email-glider@google.com> <1469719879-11761-3-git-send-email-glider@google.com> From: Andrey Ryabinin Message-ID: <579F62D3.8030605@virtuozzo.com> Date: Mon, 1 Aug 2016 17:55:15 +0300 MIME-Version: 1.0 In-Reply-To: <1469719879-11761-3-git-send-email-glider@google.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Alexander Potapenko , dvyukov@google.com, kcc@google.com, adech.fo@gmail.com, cl@linux.com, akpm@linux-foundation.org, rostedt@goodmis.org, js1304@gmail.com, iamjoonsoo.kim@lge.com, kuthonuzo.luruo@hpe.com Cc: kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org On 07/28/2016 06:31 PM, Alexander Potapenko wrote: > When free_meta_offset is not zero, it is usually aligned on 4 bytes, > because the size of preceding kasan_alloc_meta is aligned on 4 bytes. > As a result, accesses to kasan_free_meta fields may be misaligned. > > Signed-off-by: Alexander Potapenko > --- > mm/kasan/kasan.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c > index 6845f92..0379551 100644 > --- a/mm/kasan/kasan.c > +++ b/mm/kasan/kasan.c > @@ -390,7 +390,8 @@ void kasan_cache_create(struct kmem_cache *cache, size_t *size, > /* Add free meta. */ > if (cache->flags & SLAB_DESTROY_BY_RCU || cache->ctor || > cache->object_size < sizeof(struct kasan_free_meta)) { > - cache->kasan_info.free_meta_offset = *size; > + cache->kasan_info.free_meta_offset = > + ALIGN(*size, sizeof(void *)); This cannot work. I slightly changed metadata layout in http://lkml.kernel.org/g/<1470062715-14077-5-git-send-email-aryabinin@virtuozzo.com> which should also fix UBSAN's complain. > *size += sizeof(struct kasan_free_meta); > } > redzone_adjust = optimal_redzone(cache->object_size) - > -- 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