CAN: read only up to 8 bytes

If HAL implementation writes more than 8 bytes of data, error immediately.
CANMessage defines only 8 bytes of data, lenght cannot be > 8.

This fixes ARMmbed#15361

Signed-off-by: Martin Kojtal <martin.kojtal@arm.com>

drivers/source/CAN.cpp

@@ -19,6 +19,7 @@
 #if DEVICE_CAN
 
 #include "platform/mbed_power_mgmt.h"
+#include "platform/mbed_error.h"
 
 namespace mbed {
 
@@ -82,6 +83,9 @@ int CAN::read(CANMessage &msg, int handle)
 {
  lock();
  int ret = can_read(&_can, &msg, handle);
+ if (msg.len > 8) {
+ MBED_ERROR(MBED_MAKE_ERROR(MBED_MODULE_DRIVER_CAN, MBED_ERROR_CODE_READ_FAILED), "Read tried to write more than 8 bytes");
+ }
  unlock();
  return ret;
 }