Re: [PATCH 9/9] serial: xuartps: Fix out-of-bounds access through DT alias

From: Michal Simek
Date: Tue Feb 20 2018 - 05:22:31 EST


On 20.2.2018 10:40, Geert Uytterhoeven wrote:
> The cdns_uart_port[] array is indexed using a value derived from the
> "serialN" alias in DT, which may lead to an out-of-bounds access.
>
> Fix this by adding a range check.
>
> Fixes: 1f118c02a1819856 ("serial: xuartps: Fix out-of-bounds access through DT alias")

I didn't find this sha1 - patch name is this one.

> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> ---
> drivers/tty/serial/xilinx_uartps.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
> index b9b2bc76bcac606c..abcb4d09a2d866d0 100644
> --- a/drivers/tty/serial/xilinx_uartps.c
> +++ b/drivers/tty/serial/xilinx_uartps.c
> @@ -1110,7 +1110,7 @@ static struct uart_port *cdns_uart_get_port(int id)
> struct uart_port *port;
>
> /* Try the given port id if failed use default method */
> - if (cdns_uart_port[id].mapbase != 0) {
> + if (id < CDNS_UART_NR_PORTS && cdns_uart_port[id].mapbase != 0) {
> /* Find the next unused port */
> for (id = 0; id < CDNS_UART_NR_PORTS; id++)
> if (cdns_uart_port[id].mapbase == 0)
>

Below should be better fix for this driver.

Thanks,
Michal

diff --git a/drivers/tty/serial/xilinx_uartps.c
b/drivers/tty/serial/xilinx_uartps.c
index b9b2bc76bcac..b77c6477ed93 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1109,6 +1109,9 @@ static struct uart_port *cdns_uart_get_port(int id)
{
struct uart_port *port;

+ if (id >= CDNS_UART_NR_PORTS)
+ return NULL;
+
/* Try the given port id if failed use default method */
if (cdns_uart_port[id].mapbase != 0) {
/* Find the next unused port */
@@ -1117,9 +1120,6 @@ static struct uart_port *cdns_uart_get_port(int id)
break;
}

- if (id >= CDNS_UART_NR_PORTS)
- return NULL;
-
port = &cdns_uart_port[id];

/* At this point, we've got an empty uart_port struct,
initialize it */