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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C0C1C433EF for ; Thu, 28 Apr 2022 14:04:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240073AbiD1OH4 (ORCPT ); Thu, 28 Apr 2022 10:07:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37666 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348000AbiD1OGv (ORCPT ); Thu, 28 Apr 2022 10:06:51 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 30AB1B53E6 for ; Thu, 28 Apr 2022 07:03:17 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BB6BF1474; Thu, 28 Apr 2022 07:03:16 -0700 (PDT) Received: from e120937-lin (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7BD7D3F5A1; Thu, 28 Apr 2022 07:03:15 -0700 (PDT) Date: Thu, 28 Apr 2022 15:03:05 +0100 From: Cristian Marussi To: Sudeep Holla Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, james.quinlan@broadcom.com, Jonathan.Cameron@huawei.com, f.fainelli@gmail.com, etienne.carriere@linaro.org, vincent.guittot@linaro.org, souvik.chakravarty@arm.com Subject: Re: [PATCH 04/22] firmware: arm_scmi: Validate BASE_DISCOVER_LIST_PROTOCOLS reply Message-ID: References: <20220330150551.2573938-1-cristian.marussi@arm.com> <20220330150551.2573938-5-cristian.marussi@arm.com> <20220428100729.qlzl5lkkn2r5u3ra@bogus> <20220428135504.lt3bjq4sz7uktca6@bogus> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220428135504.lt3bjq4sz7uktca6@bogus> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 28, 2022 at 02:55:04PM +0100, Sudeep Holla wrote: > On Thu, Apr 28, 2022 at 02:45:07PM +0100, Cristian Marussi wrote: > > On Thu, Apr 28, 2022 at 11:07:29AM +0100, Sudeep Holla wrote: > > > On Wed, Mar 30, 2022 at 04:05:33PM +0100, Cristian Marussi wrote: > > > > Do not blindly trust SCMI backend server reply about list of implemented > > > > protocols, instead validate the reported length of the list of protocols > > > > against the real payload size of the message reply. > > > > > > > > Fixes: b6f20ff8bd9 ("firmware: arm_scmi: add common infrastructure and support for base protocol") > > > > Signed-off-by: Cristian Marussi > > > > --- > > > > drivers/firmware/arm_scmi/base.c | 21 +++++++++++++++++++++ > > > > 1 file changed, 21 insertions(+) > > > > > > > > diff --git a/drivers/firmware/arm_scmi/base.c b/drivers/firmware/arm_scmi/base.c > > > > index f279146f8110..c1165d1282ef 100644 > > > > --- a/drivers/firmware/arm_scmi/base.c > > > > +++ b/drivers/firmware/arm_scmi/base.c > > > > @@ -189,6 +189,9 @@ scmi_base_implementation_list_get(const struct scmi_protocol_handle *ph, > > > > list = t->rx.buf + sizeof(*num_ret); > > > > > > > > do { > > > > + size_t real_list_sz; > > > > + u32 calc_list_sz; > > > > + > > > > /* Set the number of protocols to be skipped/already read */ > > > > *num_skip = cpu_to_le32(tot_num_ret); > > > > > > > > @@ -202,6 +205,24 @@ scmi_base_implementation_list_get(const struct scmi_protocol_handle *ph, > > > > break; > > > > } > > > > > > > > + if (t->rx.len < (sizeof(u32) * 2)) { > > > > + dev_err(dev, "Truncated reply - rx.len:%zd\n", > > > > + t->rx.len); > > > > + ret = -EPROTO; > > > > + break; > > > > + } > > > > + > > > > + real_list_sz = t->rx.len - sizeof(u32); > > > > + calc_list_sz = ((loop_num_ret / sizeof(u32)) + > > > > + !!(loop_num_ret % sizeof(u32))) * sizeof(u32); > > > > > > Any reason this can't be (loop_num_ret - 1) / sizeof(u32) + 1 ? > > > > > > > At first sight could be fine with your easier version BUT what if loop_num_ret > > is returned as zero ? > > > > real_list_sz should be ZERO length and calc_list_sz > > > > im my version: > > > > calc_list_sz = ((0/4) +!!(0%4)) * 4 ===>> 0 > > > > while in the simplified one gets calculated wrong: > > > > calc_list_sz = (0-1)/4 + 1 ====> 1 > > > > ...moreover being both loop_num_ret and calc_list_sz unsigned I am even > > not so sure about implicit casting messing things up evenm more :D > > > > So I sticked to the more convoluted approach :D > > > > ....Have I missed something else ? > > > > Right, but shouldn't we break if it 0 much earlier. It must not happen with > your new logic and even if it does, wouldn't it be better to break earlier ? > Fine for me. Thanks, Cristian