From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 2A030A04BC; Fri, 9 Oct 2020 18:37:49 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id E66EA1C43D; Fri, 9 Oct 2020 18:37:47 +0200 (CEST) Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [217.70.183.198]) by dpdk.org (Postfix) with ESMTP id E1EE31C2F9 for ; Fri, 9 Oct 2020 18:37:46 +0200 (CEST) X-Originating-IP: 86.254.165.59 Received: from u256.net (lfbn-poi-1-843-59.w86-254.abo.wanadoo.fr [86.254.165.59]) (Authenticated sender: grive@u256.net) by relay6-d.mail.gandi.net (Postfix) with ESMTPSA id 03E04C0008; Fri, 9 Oct 2020 16:37:44 +0000 (UTC) Date: Fri, 9 Oct 2020 18:37:39 +0200 From: =?utf-8?Q?Ga=C3=ABtan?= Rivet To: Ferruh Yigit Cc: Bruce Richardson , Olivier Matz , Ciara Loftus , dev@dpdk.org Message-ID: <20201009163739.7iu3ce2otdyrxe4p@u256.net> References: <20201007090137.5121-1-ciara.loftus@intel.com> <20201007095131.GQ21395@platinum> <20201007102638.GB680@bricha3-MOBL.ger.corp.intel.com> <20201007102812.GC680@bricha3-MOBL.ger.corp.intel.com> <20201009103630.jicsmryvgsxc72bl@u256.net> <8f533e07-c6bf-46bd-2b42-dc5d9a9c3b42@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8f533e07-c6bf-46bd-2b42-dc5d9a9c3b42@intel.com> Subject: Re: [dpdk-dev] [PATCH] net/af_xdp: use snprintf instead of strncpy X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 09/10/20 11:59 +0100, Ferruh Yigit wrote: > On 10/9/2020 11:36 AM, Gaëtan Rivet wrote: > > On 07/10/20 12:45 +0100, Ferruh Yigit wrote: > > > On 10/7/2020 11:28 AM, Bruce Richardson wrote: > > > > On Wed, Oct 07, 2020 at 11:26:38AM +0100, Bruce Richardson wrote: > > > > > On Wed, Oct 07, 2020 at 11:51:31AM +0200, Olivier Matz wrote: > > > > > > On Wed, Oct 07, 2020 at 10:40:32AM +0100, Ferruh Yigit wrote: > > > > > > > On 10/7/2020 10:01 AM, Ciara Loftus wrote: > > > > > > > > strncpy may leave the destination buffer not NULL terminated so use > > > > > > > > snprintf instead. > > > > > > > > > > > > > > What do you think using 'strlcpy'? > > > > > > > > > > > > Or even better, rte_strscpy() > > > > > > https://git.dpdk.org/dpdk/commit/?id=b0236c7cf761 > > > > > > > > > > > I think this is largely a matter of preference, and unless there is a good > > > > > reason not to, I tend towards strlcpy as the older and more common (till > > > > > now) interface. The main thing is just to use a function that will > > > > > guarantee dest is null-terminated here, and both strlcpy and strscpy meet > > > > > that criteria. > > > > > > > > > I'd also add that strlcpy is more likely to be recognised by tools like > > > > coverity, compared to rte_strscpy which is DPDK-specific. > > > > > > > > > > +1 to 'strlcpy' > > > > Using strlcpy will be more recognized by static analyzer indeed. > > > > But strscpy API is better: > > > > * It helps checking string truncation by making it easier: > > > > if (strlcpy(dst, src, dstsize) >= dstsize) > > /* Dev + reviewer needs to think about using >= and not >, dstsize is > > * repeated so either dst is an array or it needs a dedicated variable. > > * Deal with truncation. > > */ > > > > if (rte_strscpy(dst, src, dstsize) < 0) > > /* deal with truncation. */ > > > > * It is safer when dealing with unknown data source. strlcpy will always > > read all of src, because the API (uselessly) defines the return value > > to strlen(src). > > > > Having yet another string copy function is contentious, but we can avoid > > using worse API to please tools. > > > > And detecting string truncation *is* helpful. String are used as IDs in > > DPDK for some objects. Using strlcpy / snprintf at least protects from > > buffer overflow, which is a bare minimum. A good implementation would > > also warn the user about a config error / memory corruption happening > > sooner. > > > > In any case, sure to fix a sanity check strlcpy / snprintf will work. > > > > I also think 'strscpy' is better API, and we had similar discussion before > [1] and the decision was to prefer 'strlcpy'. > > [1] http://inbox.dpdk.org/dev/b800d417-c33d-af4e-b506-8f31ae919410@intel.com/#t Good memory! I hadn't seen this thread, thanks. -- Gaëtan