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Subject: Re: [PATCH v4] HID: ft260: improve error handling of
 ft260_hid_feature_report_get()
To:     Michael Zaidman <michael.zaidman@gmail.com>, jikos@kernel.org,
        benjamin.tissoires@redhat.com
Cc:     linux-i2c@vger.kernel.org, linux-input@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20210511101208.16401-1-michael.zaidman@gmail.com>
From:   Tom Rix <trix@redhat.com>
Message-ID: <30c2857d-5094-402e-25a8-48f5be83fa3f@redhat.com>
Date:   Tue, 11 May 2021 06:10:36 -0700
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Generally change is fine.

a nit below.

On 5/11/21 3:12 AM, Michael Zaidman wrote:
> Fixes: 6a82582d9fa4 ("HID: ft260: add usb hid to i2c host bridge driver")
>
> The ft260_hid_feature_report_get() checks if the return size matches
> the requested size. But the function can also fail with at least -ENOMEM.
> Add the < 0 checks.
>
> In ft260_hid_feature_report_get(), do not do the memcpy to the caller's
> buffer if there is an error.
>
> ---
> v4   Fixed commit message
> ---
> v3   Simplify and optimize the changes
> ---
> v2:  add unlikely()'s for error conditions
> ---
>
> Signed-off-by: Tom Rix <trix@redhat.com>
> Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com>
> ---
>   drivers/hid/hid-ft260.c | 24 ++++++++++++------------
>   1 file changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c
> index 047aa85a7c83..7f4cb823129e 100644
> --- a/drivers/hid/hid-ft260.c
> +++ b/drivers/hid/hid-ft260.c
> @@ -249,7 +249,10 @@ static int ft260_hid_feature_report_get(struct hid_device *hdev,
>   
>   	ret = hid_hw_raw_request(hdev, report_id, buf, len, HID_FEATURE_REPORT,
>   				 HID_REQ_GET_REPORT);
> -	memcpy(data, buf, len);
> +	if (likely(ret == len))
> +		memcpy(data, buf, len);
> +	else if (ret >= 0)
> +		ret = -EIO;
>   	kfree(buf);
>   	return ret;
>   }
> @@ -298,7 +301,7 @@ static int ft260_xfer_status(struct ft260_device *dev)
>   
>   	ret = ft260_hid_feature_report_get(hdev, FT260_I2C_STATUS,
>   					   (u8 *)&report, sizeof(report));
> -	if (ret < 0) {
> +	if (unlikely(ret < 0)) {
>   		hid_err(hdev, "failed to retrieve status: %d\n", ret);
>   		return ret;
>   	}
> @@ -720,10 +723,9 @@ static int ft260_get_system_config(struct hid_device *hdev,
>   
>   	ret = ft260_hid_feature_report_get(hdev, FT260_SYSTEM_SETTINGS,
>   					   (u8 *)cfg, len);
> -	if (ret != len) {
> +	if (ret < 0) {

nit: should be consistent and use unlikely(ret < 0) for this and other 
similar checks.

Tom

>   		hid_err(hdev, "failed to retrieve system status\n");
> -		if (ret >= 0)
> -			return -EIO;
> +		return ret;
>   	}
>   	return 0;
>   }
> @@ -776,8 +778,8 @@ static int ft260_byte_show(struct hid_device *hdev, int id, u8 *cfg, int len,
>   	int ret;
>   
>   	ret = ft260_hid_feature_report_get(hdev, id, cfg, len);
> -	if (ret != len && ret >= 0)
> -		return -EIO;
> +	if (ret < 0)
> +		return ret;
>   
>   	return scnprintf(buf, PAGE_SIZE, "%hi\n", *field);
>   }
> @@ -788,8 +790,8 @@ static int ft260_word_show(struct hid_device *hdev, int id, u8 *cfg, int len,
>   	int ret;
>   
>   	ret = ft260_hid_feature_report_get(hdev, id, cfg, len);
> -	if (ret != len && ret >= 0)
> -		return -EIO;
> +	if (ret < 0)
> +		return ret;
>   
>   	return scnprintf(buf, PAGE_SIZE, "%hi\n", le16_to_cpu(*field));
>   }
> @@ -940,10 +942,8 @@ static int ft260_probe(struct hid_device *hdev, const struct hid_device_id *id)
>   
>   	ret = ft260_hid_feature_report_get(hdev, FT260_CHIP_VERSION,
>   					   (u8 *)&version, sizeof(version));
> -	if (ret != sizeof(version)) {
> +	if (ret < 0) {
>   		hid_err(hdev, "failed to retrieve chip version\n");
> -		if (ret >= 0)
> -			ret = -EIO;
>   		goto err_hid_close;
>   	}
>