HID: hid-goodix: Fix type promotion bug in goodix_hid_get_raw_report()

The issue is GOODIX_HID_PKG_LEN_SIZE is defined as sizeof(u16) which is
type size_t.  However, goodix_hid_check_ack_status() returns negative
error codes or potentially a positive but invalid length which is too
small.  So when we compare "if ((response_data_len <=
GOODIX_HID_PKG_LEN_SIZE)" then negative error codes are type promoted to
size_t and counted as a positive large value and treated as valid.

It would have been easy enough to add some casting to avoid the type
promotion, however this patch takes a more thourough approach and moves
the length check into goodix_hid_check_ack_status().  Now the function
only return negative error codes or zero on success and the length
pointer is never set to an invalid length.

Fixes: 75e16c8ce283 ("HID: hid-goodix: Add Goodix HID-over-SPI driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

diff --git a/drivers/hid/hid-goodix-spi.c b/drivers/hid/hid-goodix-spi.c
index 5103bf0..de655f7 100644 (file)
--- a/drivers/hid/hid-goodix-spi.c
+++ b/drivers/hid/hid-goodix-spi.c
@@ -335,11 +335,12 @@ static void goodix_hid_close(struct hid_device *hid)
 }
 
 /* Return date length of response data */
-static int goodix_hid_check_ack_status(struct goodix_ts_data *ts)
+static int goodix_hid_check_ack_status(struct goodix_ts_data *ts, u32 *resp_len)
 {
        struct goodix_hid_report_header hdr;
        int retry = 20;
        int error;
+       int len;
 
        while (retry--) {
                /*
@@ -349,8 +350,15 @@ static int goodix_hid_check_ack_status(struct goodix_ts_data *ts)
                 */
                error = goodix_spi_read(ts, ts->hid_report_addr,
                                        &hdr, sizeof(hdr));
-               if (!error && (hdr.flag & GOODIX_HID_ACK_READY_FLAG))
-                       return le16_to_cpu(hdr.size);
+               if (!error && (hdr.flag & GOODIX_HID_ACK_READY_FLAG)) {
+                       len = le16_to_cpu(hdr.size);
+                       if (len < GOODIX_HID_PKG_LEN_SIZE) {
+                               dev_err(ts->dev, "hrd.size too short: %d", len);
+                               return -EINVAL;
+                       }
+                       *resp_len = len;
+                       return 0;
+               }
 
                /* Wait 10ms for another try */
                usleep_range(10000, 11000);
@@ -383,7 +391,7 @@ static int goodix_hid_get_raw_report(struct hid_device *hid,
        u16 cmd_register = le16_to_cpu(ts->hid_desc.cmd_register);
        u8 tmp_buf[GOODIX_HID_MAX_INBUF_SIZE];
        int tx_len = 0, args_len = 0;
-       int response_data_len;
+       u32 response_data_len;
        u8 args[3];
        int error;
 
@@ -434,9 +442,9 @@ static int goodix_hid_get_raw_report(struct hid_device *hid,
                return 0;
 
        /* Step2: check response data status */
-       response_data_len = goodix_hid_check_ack_status(ts);
-       if (response_data_len <= GOODIX_HID_PKG_LEN_SIZE)
-               return -EINVAL;
+       error = goodix_hid_check_ack_status(ts, &response_data_len);
+       if (error)
+               return error;
 
        len = min(len, response_data_len - GOODIX_HID_PKG_LEN_SIZE);
        /* Step3: read response data(skip 2bytes of hid pkg length) */