USB: misc: cypress_cy7c63: check for short transfer

commit 49cd2f4 upstream.

As we process the second byte of a control transfer, transfers
of less than 2 bytes must be discarded.

This bug is as old as the driver.

SIgned-off-by: Oliver Neukum <oneukum@suse.com>
CC: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240912125449.1030536-1-oneukum@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: oneukum

drivers/usb/misc/cypress_cy7c63.c

@@ -88,6 +88,9 @@ static int vendor_command(struct cypress *dev, unsigned char request,
 				 USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_OTHER,
 				 address, data, iobuf, CYPRESS_MAX_REQSIZE,
 				 USB_CTRL_GET_TIMEOUT);
+	/* we must not process garbage */
+	if (retval < 2)
+		goto err_buf;
 
 	/* store returned data (more READs to be added) */
 	switch (request) {
@@ -107,6 +110,7 @@ static int vendor_command(struct cypress *dev, unsigned char request,
 			break;
 	}
 
+err_buf:
 	kfree(iobuf);
 error:
 	return retval;