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 987AAC433F5 for ; Tue, 31 May 2022 11:03:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343676AbiEaLDD (ORCPT ); Tue, 31 May 2022 07:03:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57232 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238251AbiEaLDB (ORCPT ); Tue, 31 May 2022 07:03:01 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id EE8B1994D2 for ; Tue, 31 May 2022 04:02:59 -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 8C23C23A; Tue, 31 May 2022 04:02:59 -0700 (PDT) Received: from [10.57.81.38] (unknown [10.57.81.38]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D57073F73D; Tue, 31 May 2022 04:02:58 -0700 (PDT) Message-ID: <1cdf5131-a67b-7297-ad75-49b53f2da293@arm.com> Date: Tue, 31 May 2022 12:02:53 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH 2/2] firmware: arm_scmi: Fix pointers arithmetic in Base protocol Content-Language: en-GB To: Cristian Marussi , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Sudeep Holla References: <20220530115237.277077-1-cristian.marussi@arm.com> <20220530115237.277077-2-cristian.marussi@arm.com> From: Robin Murphy In-Reply-To: <20220530115237.277077-2-cristian.marussi@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022-05-30 12:52, Cristian Marussi wrote: > Fix a possible undefined behaviour involving pointer arithmetic in Base > protocol scmi_base_implementation_list_get(). > > cppcheck complains with: > > drivers/firmware/arm_scmi/base.c:190:19: warning: 't->rx.buf' is of type 'void *'. When using void pointers in calculations, the behaviour is undefined. [arithOperationsOnVoidPointer] > list = t->rx.buf + sizeof(*num_ret); Except we use GNU C, where it is well-defined[1]. We use void pointer arithmetic *all over* Linux, so there really isn't any valid argument that it could be problematic. If this was a common SCMI library intended to be portable then the patch would seem more reasonable, but in Linux-specific driver code it's just pointless churn. Cheers, Robin. [1] https://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html > Fixes: b6f20ff8bd94 ("firmware: arm_scmi: add common infrastructure and support for base protocol") > Cc: Sudeep Holla > Signed-off-by: Cristian Marussi > --- > drivers/firmware/arm_scmi/base.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/firmware/arm_scmi/base.c b/drivers/firmware/arm_scmi/base.c > index 20fba7370f4e..6d6214d9e68c 100644 > --- a/drivers/firmware/arm_scmi/base.c > +++ b/drivers/firmware/arm_scmi/base.c > @@ -187,7 +187,7 @@ scmi_base_implementation_list_get(const struct scmi_protocol_handle *ph, > > num_skip = t->tx.buf; > num_ret = t->rx.buf; > - list = t->rx.buf + sizeof(*num_ret); > + list = ((u8 *)t->rx.buf) + sizeof(*num_ret); > > do { > size_t real_list_sz;