2021-12-16 09:44:33

by Jiasheng Jiang

Subject: [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 <[email protected]>
---
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;
+ }
+
priv->chan_rx = chan;
}

--
2.25.1

2021-12-16 10:18:35

by Greg Kroah-Hartman

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

On Thu, Dec 16, 2021 at 05:44:08PM +0800, Jiasheng Jiang wrote:
> 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 <[email protected]>
> ---
> 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;

You are not returning an error, what happens when this buffer is later
attempted to be used?

How did you test this change?

thanks,

greg k-h