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=-9.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 CBBA9C55179 for ; Tue, 27 Oct 2020 17:08:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 864CF21D24 for ; Tue, 27 Oct 2020 17:08:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1816651AbgJ0RIQ (ORCPT ); Tue, 27 Oct 2020 13:08:16 -0400 Received: from smtprelay0063.hostedemail.com ([216.40.44.63]:47840 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1816629AbgJ0RIO (ORCPT ); Tue, 27 Oct 2020 13:08:14 -0400 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay08.hostedemail.com (Postfix) with ESMTP id 45489182CED2A; Tue, 27 Oct 2020 17:08:10 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: rake71_590ddfb2727d X-Filterd-Recvd-Size: 4916 Received: from XPS-9350.home (unknown [47.151.133.149]) (Authenticated sender: joe@perches.com) by omf05.hostedemail.com (Postfix) with ESMTPA; Tue, 27 Oct 2020 17:08:04 +0000 (UTC) Message-ID: <2767969b94fd66db1fb0fc13b5783ae65b7deb2f.camel@perches.com> Subject: Re: [PATCH 3/8] vhost: vringh: use krealloc_array() From: Joe Perches To: Bartosz Golaszewski Cc: "Michael S. Tsirkin" , Bartosz Golaszewski , Andy Shevchenko , Sumit Semwal , Gustavo Padovan , Christian =?ISO-8859-1?Q?K=F6nig?= , Mauro Carvalho Chehab , Borislav Petkov , Tony Luck , James Morse , Robert Richter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Alexander Shishkin , Linus Walleij , Jason Wang , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Jaroslav Kysela , Takashi Iwai , linux-media , linux-drm , linaro-mm-sig@lists.linaro.org, LKML , linux-edac@vger.kernel.org, linux-gpio , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev , linux-mm@kvack.org, Linux-ALSA Date: Tue, 27 Oct 2020 10:08:02 -0700 In-Reply-To: References: <20201027121725.24660-1-brgl@bgdev.pl> <20201027121725.24660-4-brgl@bgdev.pl> <20201027112607-mutt-send-email-mst@kernel.org> <685d850347a1191bba8ba7766fc409b140d18f03.camel@perches.com> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.38.1-1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, 2020-10-27 at 17:58 +0100, Bartosz Golaszewski wrote: > On Tue, Oct 27, 2020 at 5:50 PM Joe Perches wrote: > > > > On Tue, 2020-10-27 at 11:28 -0400, Michael S. Tsirkin wrote: > > > On Tue, Oct 27, 2020 at 01:17:20PM +0100, Bartosz Golaszewski wrote: > > > > From: Bartosz Golaszewski > > > > > > > > Use the helper that checks for overflows internally instead of manually > > > > calculating the size of the new array. > > > > > > > > Signed-off-by: Bartosz Golaszewski > > > > > > No problem with the patch, it does introduce some symmetry in the code. > > > > Perhaps more symmetry by using kmemdup > > --- > >  drivers/vhost/vringh.c | 23 ++++++++++------------- > >  1 file changed, 10 insertions(+), 13 deletions(-) > > > > diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c > > index 8bd8b403f087..99222a3651cd 100644 > > --- a/drivers/vhost/vringh.c > > +++ b/drivers/vhost/vringh.c > > @@ -191,26 +191,23 @@ static int move_to_indirect(const struct vringh *vrh, > >  static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp) > >  { > >         struct kvec *new; > > - unsigned int flag, new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2; > > + size_t new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2; > > + size_t size; > > > >         if (new_num < 8) > >                 new_num = 8; > > > > - flag = (iov->max_num & VRINGH_IOV_ALLOCATED); > > - if (flag) > > - new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp); > > - else { > > - new = kmalloc_array(new_num, sizeof(struct iovec), gfp); > > - if (new) { > > - memcpy(new, iov->iov, > > - iov->max_num * sizeof(struct iovec)); > > - flag = VRINGH_IOV_ALLOCATED; > > - } > > - } > > + if (unlikely(check_mul_overflow(new_num, sizeof(struct iovec), &size))) > > + return -ENOMEM; > > + > > The whole point of using helpers such as kmalloc_array() is not doing > these checks manually. Tradeoffs for in readability for overflow and not mistyping or doing the multiplication of iov->max_num * sizeof(struct iovec) twice. Just fyi: the realloc doesn't do a multiplication overflow test as written so the suggestion is slightly more resistant to defect.