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?