HID: i2c-hid: fix size check and type usage

BugLink: http://bugs.launchpad.net/bugs/1768429

commit ac75a041 upstream.

When convert char array with signed int, if the inbuf[x] is negative then
upper bits will be set to 1. Fix this by using u8 instead of char.

ret_size has to be at least 3, hid_input_report use it after minus 2 bytes.

Cc: stable@vger.kernel.org
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/hid/i2c-hid/i2c-hid.c

@@ -137,10 +137,10 @@ struct i2c_hid {
 						   * register of the HID
 						   * descriptor. */
 	unsigned int		bufsize;	/* i2c buffer size */
-	char			*inbuf;		/* Input buffer */
-	char			*rawbuf;	/* Raw Input buffer */
-	char			*cmdbuf;	/* Command buffer */
-	char			*argsbuf;	/* Command arguments buffer */
+	u8			*inbuf;		/* Input buffer */
+	u8			*rawbuf;	/* Raw Input buffer */
+	u8			*cmdbuf;	/* Command buffer */
+	u8			*argsbuf;	/* Command arguments buffer */
 
 	unsigned long		flags;		/* device flags */
 
@@ -387,7 +387,8 @@ static int i2c_hid_hwreset(struct i2c_client *client)
 
 static void i2c_hid_get_input(struct i2c_hid *ihid)
 {
-	int ret, ret_size;
+	int ret;
+	u32 ret_size;
 	int size = le16_to_cpu(ihid->hdesc.wMaxInputLength);
 
 	if (size > ihid->bufsize)
@@ -412,7 +413,7 @@ static void i2c_hid_get_input(struct i2c_hid *ihid)
 		return;
 	}
 
-	if (ret_size > size) {
+	if ((ret_size > size) || (ret_size <= 2)) {
 		dev_err(&ihid->client->dev, "%s: incomplete report (%d/%d)\n",
 			__func__, size, ret_size);
 		return;