Re: [PATCH] serial: pch_uart: potential dereference of null pointer

The return value of dma_alloc_coherent() needs to be checked.
To avoid dereference of null pointer in case of the failure of alloc.

Fixes: ab4382d27412 ("tty: move drivers/serial/ to drivers/tty/serial/")
Signed-off-by: Jiasheng Jiang <redacted>
---
 drivers/tty/serial/pch_uart.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index f0351e6f0ef6..2ee1c4d6f177 100644
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c

@@ -745,6 +745,12 @@ static void pch_request_dma(struct uart_port *port)
 	/* Get Consistent memory for DMA */
 	priv->rx_buf_virt = dma_alloc_coherent(port->dev, port->fifosize,
 				    &priv->rx_buf_dma, GFP_KERNEL);
+	if (!priv->rx_buf_virt) {
+		dma_release_channel(priv->chan_tx);
+		priv->chan_tx = NULL;
+		return;