linux-kernel - Re: [PATCH v2 net] nfp: cast sizeof() to int when comparing with error code

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Message-ID: <ff0b2834b771a467246b9f7c1b4600c38f5bb463.camel@perches.com>
Date:   Mon, 25 Jun 2018 19:10:59 -0700
From:   Joe Perches <joe@...ches.com>
To:     Chengguang Xu <cgxu519@....com>, jakub.kicinski@...ronome.com,
        davem@...emloft.net, LKML <linux-kernel@...r.kernel.org>,
        Julia Lawall <julia.lawall@...6.fr>,
        cocci <cocci@...teme.lip6.fr>
Cc:     oss-drivers@...ronome.com, netdev@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-input <linux-input@...r.kernel.org>,
        linux-s390 <linux-s390@...r.kernel.org>
Subject: Re: [PATCH v2 net] nfp: cast sizeof() to int when comparing with
 error code

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?