From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f199.google.com (mail-qt0-f199.google.com [209.85.216.199]) by kanga.kvack.org (Postfix) with ESMTP id 452E96B6E25 for ; Tue, 4 Sep 2018 11:18:54 -0400 (EDT) Received: by mail-qt0-f199.google.com with SMTP id u45-v6so4310794qte.12 for ; Tue, 04 Sep 2018 08:18:54 -0700 (PDT) Received: from a9-54.smtp-out.amazonses.com (a9-54.smtp-out.amazonses.com. [54.240.9.54]) by mx.google.com with ESMTPS id d5-v6si792428qkf.371.2018.09.04.08.18.53 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 04 Sep 2018 08:18:53 -0700 (PDT) Date: Tue, 4 Sep 2018 15:18:52 +0000 From: Christopher Lameter Subject: Re: [PATCH v6 11/18] khwasan, mm: perform untagged pointers comparison in krealloc In-Reply-To: Message-ID: <01000165a52a3a0b-f9832a6e-358f-4400-b941-47984458b754-000000@email.amazonses.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrey Konovalov Cc: linux-mm@kvack.org Reviewed-by: Christoph Lameter On Wed, 29 Aug 2018, Andrey Konovalov wrote: > The krealloc function checks where the same buffer was reused or a new one > allocated by comparing kernel pointers. KHWASAN changes memory tag on the > krealloc'ed chunk of memory and therefore also changes the pointer tag of > the returned pointer. Therefore we need to perform comparison on untagged > (with tags reset) pointers to check whether it's the same memory region or > not. > > Signed-off-by: Andrey Konovalov > --- > mm/slab_common.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 3abfa0f86118..0d588dfebd7d 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -1513,7 +1513,7 @@ void *krealloc(const void *p, size_t new_size, gfp_t flags) > } > > ret = __do_krealloc(p, new_size, flags); > - if (ret && p != ret) > + if (ret && khwasan_reset_tag(p) != khwasan_reset_tag(ret)) > kfree(p); > > return ret; >