From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julia Lawall Subject: Re: [PATCH v2 net] nfp: cast sizeof() to int when comparing with error code Date: Tue, 26 Jun 2018 09:21:52 +0200 (CEST) Message-ID: References: <20180626011631.22717-1-cgxu519@gmx.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: Chengguang Xu , jakub.kicinski@netronome.com, davem@davemloft.net, LKML , cocci , oss-drivers@netronome.com, netdev@vger.kernel.org, Dmitry Torokhov , linux-input , linux-s390 To: Joe Perches Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Mon, 25 Jun 2018, Joe Perches wrote: > On Tue, 2018-06-26 at 09:16 +0800, Chengguang Xu wrote: > > sizeof() will return unsigned value so in the error check > > negative error code will be always larger than sizeof(). > > This looks like a general class of error in the kernel > where a signed result that could be returning a -errno > is tested against < or <= sizeof() > > A couple examples: > > drivers/input/mouse/elan_i2c_smbus.c: > > len = i2c_smbus_read_block_data(client, > ETP_SMBUS_IAP_PASSWORD_READ, > val); > if (len < sizeof(u16)) { > > i2c_smbus_read_block_data can return a negative errno > > > net/smc/smc_clc.c: > > len = kernel_sendmsg(smc->clcsock, &msg, &vec, 1, > sizeof(struct smc_clc_msg_decline)); > if (len < sizeof(struct smc_clc_msg_decline)) > > where kernel_sendmsg can return a negative errno > > There are probably others, I didn't look hard. > > Perhaps a cocci script to find these could be generated? Currently there is a rule for comparison of unsigneds to 0. It would be reasonable to extend it for sizes. I will see what it gives. julia