spi: spi-zynqmp-gqspi: Resolved slab-out-of-bounds bug

During a transfer the driver filled the fifo with 4bytes,
even if the data that needs to be transfer is less that 4bytes.
This resulted in slab-out-of-bounds bug in KernelAddressSanitizer.

This patch resolves slab-out-of-bounds bug by filling the fifo
with the number of bytes that needs to transferred.
Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@xilinx.com>
Link: https://lore.kernel.org/r/20210416004652.2975446-4-quanyang.wang@windriver.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-zynqmp-gqspi.c

@@ -509,17 +509,19 @@ static void zynqmp_qspi_filltxfifo(struct zynqmp_qspi *xqspi, int size)
 	u32 count = 0, intermediate;
 
 	while ((xqspi->bytes_to_transfer > 0) && (count < size) && (xqspi->txbuf)) {
-		memcpy(&intermediate, xqspi->txbuf, 4);
-		zynqmp_gqspi_write(xqspi, GQSPI_TXD_OFST, intermediate);
-
 		if (xqspi->bytes_to_transfer >= 4) {
+			memcpy(&intermediate, xqspi->txbuf, 4);
 			xqspi->txbuf += 4;
 			xqspi->bytes_to_transfer -= 4;
+			count += 4;
 		} else {
+			memcpy(&intermediate, xqspi->txbuf,
+			       xqspi->bytes_to_transfer);
 			xqspi->txbuf += xqspi->bytes_to_transfer;
 			xqspi->bytes_to_transfer = 0;
+			count += xqspi->bytes_to_transfer;
 		}
-		count++;
+		zynqmp_gqspi_write(xqspi, GQSPI_TXD_OFST, intermediate);
 	}
 }