[PATCH] pch_uart: Don't panic if dmi_get_system_info returns NULL

[PATCH] pch_uart: Don't panic if dmi_get_system_info returns NULL

[Alexander Stein]

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
---
 drivers/tty/serial/pch_uart.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index f2cb750..4652109 100644
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -1397,6 +1397,7 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
 	int fifosize, base_baud;
 	int port_type;
 	struct pch_uart_driver_data *board;
+	const char *board_name;
 
 	board = &drv_dat[id->driver_data];
 	port_type = board->port_type;
@@ -1412,7 +1413,8 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
 	base_baud = 1843200; /* 1.8432MHz */
 
 	/* quirk for CM-iTC board */
-	if (strstr(dmi_get_system_info(DMI_BOARD_NAME), "CM-iTC"))
+	board_name = dmi_get_system_info(DMI_BOARD_NAME);
+	if (board_name && strstr(board_name, "CM-iTC"))
 		base_baud = 192000000; /* 192.0MHz */
 
 	switch (port_type) {
-- 
1.7.3.4

Re: [PATCH] pch_uart: Don't panic if dmi_get_system_info returns NULL

[Andrew Morton]

On Wed,  1 Jun 2011 14:11:25 +0200
Alexander Stein <alexander.stein@systec-electronic.com> wrote:

> Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
> ---
>  drivers/tty/serial/pch_uart.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
> index f2cb750..4652109 100644
> --- a/drivers/tty/serial/pch_uart.c
> +++ b/drivers/tty/serial/pch_uart.c
> @@ -1397,6 +1397,7 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
>  	int fifosize, base_baud;
>  	int port_type;
>  	struct pch_uart_driver_data *board;
> +	const char *board_name;
>  
>  	board = &drv_dat[id->driver_data];
>  	port_type = board->port_type;
> @@ -1412,7 +1413,8 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
>  	base_baud = 1843200; /* 1.8432MHz */
>  
>  	/* quirk for CM-iTC board */
> -	if (strstr(dmi_get_system_info(DMI_BOARD_NAME), "CM-iTC"))
> +	board_name = dmi_get_system_info(DMI_BOARD_NAME);
> +	if (board_name && strstr(board_name, "CM-iTC"))
>  		base_baud = 192000000; /* 192.0MHz */
>  
>  	switch (port_type) {

Please changelog your patches.

A changelog for this patch would include info such as:

a) The code doesn't panic.  I think you meant "oops due to a NULL
   pointer dereference"

b) Under what circumstances will dmi_get_system_info() return NULL?

c) Has this bug been observed in the real world, or was it from code
   inspection?  If the former, under what circumstances?

The answer to c) will allow others to decide which kernel version(s)
the fix should be merged into.

Thanks.

[PATCH v2] pch_uart: Don't oops if dmi_get_system_info returns NULL

[Alexander Stein]

This oops was observed on an Atom based board which has no BIOS, but
a bootloder which doesn't privde DMI data.

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
---
Changesin v2:
* Adjust summary
* Describe when dmi_get_system_info could return NULL

If this is ok, i will send an updated patch for the pch_phub too.

 drivers/tty/serial/pch_uart.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index f2cb750..4652109 100644
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -1397,6 +1397,7 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
 	int fifosize, base_baud;
 	int port_type;
 	struct pch_uart_driver_data *board;
+	const char *board_name;
 
 	board = &drv_dat[id->driver_data];
 	port_type = board->port_type;
@@ -1412,7 +1413,8 @@ static struct eg20t_port *pch_uart_init_port(struct pci_dev *pdev,
 	base_baud = 1843200; /* 1.8432MHz */
 
 	/* quirk for CM-iTC board */
-	if (strstr(dmi_get_system_info(DMI_BOARD_NAME), "CM-iTC"))
+	board_name = dmi_get_system_info(DMI_BOARD_NAME);
+	if (board_name && strstr(board_name, "CM-iTC"))
 		base_baud = 192000000; /* 192.0MHz */
 
 	switch (port_type) {
-- 
1.7.3.4