On Fri, May 07, 2021 at 11:37:57AM -0700, trix@xxxxxxxxxx wrote:
> From: Tom Rix <trix@xxxxxxxxxx>
>
> Static analysis reports this representative problem
>
> hid-ft260.c:787:9: warning: 4th function call argument is an
> uninitialized value
> return scnprintf(buf, PAGE_SIZE, "%hi\n", *field);
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Uses of ft260_hid_feature_report_get() check if the return size matches
> the requested size. But the function can also fail with at least -ENOMEM.
> Add the < 0 checks.
Hi Tom, thanks for catching and fixing it!
I applied the patch, built the driver, and run some tests on my HW setup -
no regression so far. But I think the fix can be improved even more, by
reducing the number of questions to one in the successful case where the
performance matters. Please see the proposal below inline.
>
> In ft260_hid_feature_report_get(), do not do the memcpy to the caller's
> buffer if there is an error.
>
> Fixes: 6a82582d9fa4 ("HID: ft260: add usb hid to i2c host bridge driver")
> Signed-off-by: Tom Rix <trix@xxxxxxxxxx>
> ---
> drivers/hid/hid-ft260.c | 19 +++++++++++++++----
> 1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c
> index 7a9ba984a75a..628fa664a10b 100644
> --- a/drivers/hid/hid-ft260.c
> +++ b/drivers/hid/hid-ft260.c
> @@ -249,7 +249,8 @@ 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 (ret == len)
> + memcpy(data, buf, len);
> kfree(buf);
> return ret;
> }
> @@ -295,12 +296,16 @@ static int ft260_xfer_status(struct ft260_device *dev)
> struct hid_device *hdev = dev->hdev;
> struct ft260_get_i2c_status_report report;
> int ret;
> + int len = sizeof(report);
>
> ret = ft260_hid_feature_report_get(hdev, FT260_I2C_STATUS,
> - (u8 *)&report, sizeof(report));
> - if (ret < 0) {
> + (u8 *)&report, len);
> + if (ret != len) {
> hid_err(hdev, "failed to retrieve status: %d\n", ret);
> - return ret;
> + if (ret >= 0)
> + return -EIO;
> + else
> + return ret;
> }
>
> dev->clock = le16_to_cpu(report.clock);
> @@ -728,6 +733,8 @@ static int ft260_get_system_config(struct hid_device *hdev,
> hid_err(hdev, "failed to retrieve system status\n");
> if (ret >= 0)
> return -EIO;
> + else
> + return ret;
> }
> return 0;
> }
> @@ -782,6 +789,8 @@ static int ft260_byte_show(struct hid_device *hdev, int id, u8 *cfg, int len,
> ret = ft260_hid_feature_report_get(hdev, id, cfg, len);
> if (ret != len && ret >= 0)
> return -EIO;
> + else if (ret < 0)
> + return ret;
Please consider the below code to reduce the number of questions to one in the "likely" case
and two in the worst-case scenario.
if (ret != len) {
if (ret >= 0)
return -EIO;
else
return ret;
}
>
> return scnprintf(buf, PAGE_SIZE, "%hi\n", *field);
> }
> @@ -794,6 +803,8 @@ static int ft260_word_show(struct hid_device *hdev, int id, u8 *cfg, int len,
> ret = ft260_hid_feature_report_get(hdev, id, cfg, len);
> if (ret != len && ret >= 0)
> return -EIO;
> + else if (ret < 0)
> + return ret;
The same.
>
> return scnprintf(buf, PAGE_SIZE, "%hi\n", le16_to_cpu(*field));
> }
> --
> 2.26.3
>
