From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A7D97C433E0 for ; Sun, 28 Jun 2020 17:37:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91D9320771 for ; Sun, 28 Jun 2020 17:37:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726614AbgF1Rhd (ORCPT ); Sun, 28 Jun 2020 13:37:33 -0400 Received: from smtprelay0008.hostedemail.com ([216.40.44.8]:44342 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726060AbgF1Rhc (ORCPT ); Sun, 28 Jun 2020 13:37:32 -0400 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay01.hostedemail.com (Postfix) with ESMTP id B07C6100E7B43; Sun, 28 Jun 2020 17:37:31 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: trade85_0d0653126e68 X-Filterd-Recvd-Size: 2324 Received: from XPS-9350.home (unknown [47.151.133.149]) (Authenticated sender: joe@perches.com) by omf16.hostedemail.com (Postfix) with ESMTPA; Sun, 28 Jun 2020 17:37:30 +0000 (UTC) Message-ID: <693db5a878ac09994e2a27c64cb14c0e552f3f50.camel@perches.com> Subject: Re: [PATCH] mm: util: update the kerneldoc for kstrdup_const() From: Joe Perches To: Bartosz Golaszewski , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Bartosz Golaszewski Date: Sun, 28 Jun 2020 10:37:29 -0700 In-Reply-To: <20200628152500.17916-1-brgl@bgdev.pl> References: <20200628152500.17916-1-brgl@bgdev.pl> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.36.2-0ubuntu1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2020-06-28 at 17:25 +0200, Bartosz Golaszewski wrote: > From: Bartosz Golaszewski > > Memory allocated with kstrdup_const() must not be passed to regular > krealloc() as it is not aware of the possibility of the chunk residing > in .rodata. Since there are no potential users of krealloc_const() > at the moment, let's just update the doc to make it explicit. Another option would be to return NULL if it's used from krealloc with a pointer into rodata --- mm/slab_common.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/mm/slab_common.c b/mm/slab_common.c index 37d48a56431d..f8b49656171b 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1683,6 +1683,9 @@ static __always_inline void *__do_krealloc(const void *p, size_t new_size, * @new_size: how many bytes of memory are required. * @flags: the type of memory to allocate. * + * If the object pointed to is in rodata (likely from kstrdup_const) + * %NULL is returned. + * * The contents of the object pointed to are preserved up to the * lesser of the new and old sizes. If @p is %NULL, krealloc() * behaves exactly like kmalloc(). If @new_size is 0 and @p is not a @@ -1694,6 +1697,9 @@ void *krealloc(const void *p, size_t new_size, gfp_t flags) { void *ret; + if (unlikely(is_kernel_rodata((unsigned long)p))) + return NULL; + if (unlikely(!new_size)) { kfree(p); return ZERO_SIZE_PTR;