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* [PATCH] tty: fix NULL pointer issue when tty_port ops is not set
@ 2019-03-21 15:43 Fabien Dessenne
  2019-03-21 17:38 ` Greg Kroah-Hartman
  0 siblings, 1 reply; 3+ messages in thread
From: Fabien Dessenne @ 2019-03-21 15:43 UTC (permalink / raw)
  To: Greg Kroah-Hartman, Jiri Slaby, linux-kernel
  Cc: Fabien Dessenne, Benjamin Gaignard

Unlike 'client_ops' which is initialized to 'default_client_ops', the
port operations 'ops' may be left to NULL.
Check the 'ops' value before checking the 'ops->x' value.

Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
---
 drivers/tty/tty_port.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 044c3cb..a9e12b3 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -325,7 +325,7 @@ static void tty_port_shutdown(struct tty_port *port, struct tty_struct *tty)
 		if (tty && C_HUPCL(tty))
 			tty_port_lower_dtr_rts(port);
 
-		if (port->ops->shutdown)
+		if (port->ops && port->ops->shutdown)
 			port->ops->shutdown(port);
 	}
 out:
@@ -398,7 +398,7 @@ EXPORT_SYMBOL_GPL(tty_port_tty_wakeup);
  */
 int tty_port_carrier_raised(struct tty_port *port)
 {
-	if (port->ops->carrier_raised == NULL)
+	if (!port->ops || !port->ops->carrier_raised)
 		return 1;
 	return port->ops->carrier_raised(port);
 }
@@ -414,7 +414,7 @@ EXPORT_SYMBOL(tty_port_carrier_raised);
  */
 void tty_port_raise_dtr_rts(struct tty_port *port)
 {
-	if (port->ops->dtr_rts)
+	if (port->ops && port->ops->dtr_rts)
 		port->ops->dtr_rts(port, 1);
 }
 EXPORT_SYMBOL(tty_port_raise_dtr_rts);
@@ -429,7 +429,7 @@ EXPORT_SYMBOL(tty_port_raise_dtr_rts);
  */
 void tty_port_lower_dtr_rts(struct tty_port *port)
 {
-	if (port->ops->dtr_rts)
+	if (port->ops && port->ops->dtr_rts)
 		port->ops->dtr_rts(port, 0);
 }
 EXPORT_SYMBOL(tty_port_lower_dtr_rts);
@@ -684,7 +684,7 @@ int tty_port_open(struct tty_port *port, struct tty_struct *tty,
 
 	if (!tty_port_initialized(port)) {
 		clear_bit(TTY_IO_ERROR, &tty->flags);
-		if (port->ops->activate) {
+		if (port->ops && port->ops->activate) {
 			int retval = port->ops->activate(port, tty);
 			if (retval) {
 				mutex_unlock(&port->mutex);
-- 
2.7.4


^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH] tty: fix NULL pointer issue when tty_port ops is not set
  2019-03-21 15:43 [PATCH] tty: fix NULL pointer issue when tty_port ops is not set Fabien Dessenne
@ 2019-03-21 17:38 ` Greg Kroah-Hartman
  2019-03-22  8:35   ` Fabien DESSENNE
  0 siblings, 1 reply; 3+ messages in thread
From: Greg Kroah-Hartman @ 2019-03-21 17:38 UTC (permalink / raw)
  To: Fabien Dessenne; +Cc: Jiri Slaby, linux-kernel, Benjamin Gaignard

On Thu, Mar 21, 2019 at 04:43:26PM +0100, Fabien Dessenne wrote:
> Unlike 'client_ops' which is initialized to 'default_client_ops', the
> port operations 'ops' may be left to NULL.
> Check the 'ops' value before checking the 'ops->x' value.
> 
> Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
> ---
>  drivers/tty/tty_port.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
> index 044c3cb..a9e12b3 100644
> --- a/drivers/tty/tty_port.c
> +++ b/drivers/tty/tty_port.c
> @@ -325,7 +325,7 @@ static void tty_port_shutdown(struct tty_port *port, struct tty_struct *tty)
>  		if (tty && C_HUPCL(tty))
>  			tty_port_lower_dtr_rts(port);
>  
> -		if (port->ops->shutdown)
> +		if (port->ops && port->ops->shutdown)
>  			port->ops->shutdown(port);
>  	}
>  out:
> @@ -398,7 +398,7 @@ EXPORT_SYMBOL_GPL(tty_port_tty_wakeup);
>   */
>  int tty_port_carrier_raised(struct tty_port *port)
>  {
> -	if (port->ops->carrier_raised == NULL)
> +	if (!port->ops || !port->ops->carrier_raised)
>  		return 1;
>  	return port->ops->carrier_raised(port);
>  }
> @@ -414,7 +414,7 @@ EXPORT_SYMBOL(tty_port_carrier_raised);
>   */
>  void tty_port_raise_dtr_rts(struct tty_port *port)
>  {
> -	if (port->ops->dtr_rts)
> +	if (port->ops && port->ops->dtr_rts)
>  		port->ops->dtr_rts(port, 1);
>  }
>  EXPORT_SYMBOL(tty_port_raise_dtr_rts);
> @@ -429,7 +429,7 @@ EXPORT_SYMBOL(tty_port_raise_dtr_rts);
>   */
>  void tty_port_lower_dtr_rts(struct tty_port *port)
>  {
> -	if (port->ops->dtr_rts)
> +	if (port->ops && port->ops->dtr_rts)
>  		port->ops->dtr_rts(port, 0);
>  }
>  EXPORT_SYMBOL(tty_port_lower_dtr_rts);
> @@ -684,7 +684,7 @@ int tty_port_open(struct tty_port *port, struct tty_struct *tty,
>  
>  	if (!tty_port_initialized(port)) {
>  		clear_bit(TTY_IO_ERROR, &tty->flags);
> -		if (port->ops->activate) {
> +		if (port->ops && port->ops->activate) {
>  			int retval = port->ops->activate(port, tty);
>  			if (retval) {
>  				mutex_unlock(&port->mutex);
> -- 
> 2.7.4
> 

Can you hit this today with any in-kernel drivers?  Or is this only for
your new code you are adding?

thanks,

greg k-h

^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [PATCH] tty: fix NULL pointer issue when tty_port ops is not set
  2019-03-21 17:38 ` Greg Kroah-Hartman
@ 2019-03-22  8:35   ` Fabien DESSENNE
  0 siblings, 0 replies; 3+ messages in thread
From: Fabien DESSENNE @ 2019-03-22  8:35 UTC (permalink / raw)
  To: Greg Kroah-Hartman; +Cc: Jiri Slaby, linux-kernel, Benjamin GAIGNARD

Hi Greg,

I do not think that any driver faces this problem.

Nevertheless I found 2 drivers declaring an 'empty' struct (wasted) to 
solve this issue:

drivers/char/ttyprintk:
static const struct tty_port_operations null_ops = { };

drivers/tty/vcc.c:
static struct tty_port_operations vcc_port_ops = { 0 };


Please let me know if you prefer I abandon this patch and use an 'empty' 
struct in the new code I add.

Or if you think that this patch is safe, feel free to ask me to update 
the two drivers listed above.


BR


Fabien



On 21/03/2019 6:38 PM, Greg Kroah-Hartman wrote:
> On Thu, Mar 21, 2019 at 04:43:26PM +0100, Fabien Dessenne wrote:
>> Unlike 'client_ops' which is initialized to 'default_client_ops', the
>> port operations 'ops' may be left to NULL.
>> Check the 'ops' value before checking the 'ops->x' value.
>>
>> Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
>> ---
>>   drivers/tty/tty_port.c | 10 +++++-----
>>   1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
>> index 044c3cb..a9e12b3 100644
>> --- a/drivers/tty/tty_port.c
>> +++ b/drivers/tty/tty_port.c
>> @@ -325,7 +325,7 @@ static void tty_port_shutdown(struct tty_port *port, struct tty_struct *tty)
>>   		if (tty && C_HUPCL(tty))
>>   			tty_port_lower_dtr_rts(port);
>>   
>> -		if (port->ops->shutdown)
>> +		if (port->ops && port->ops->shutdown)
>>   			port->ops->shutdown(port);
>>   	}
>>   out:
>> @@ -398,7 +398,7 @@ EXPORT_SYMBOL_GPL(tty_port_tty_wakeup);
>>    */
>>   int tty_port_carrier_raised(struct tty_port *port)
>>   {
>> -	if (port->ops->carrier_raised == NULL)
>> +	if (!port->ops || !port->ops->carrier_raised)
>>   		return 1;
>>   	return port->ops->carrier_raised(port);
>>   }
>> @@ -414,7 +414,7 @@ EXPORT_SYMBOL(tty_port_carrier_raised);
>>    */
>>   void tty_port_raise_dtr_rts(struct tty_port *port)
>>   {
>> -	if (port->ops->dtr_rts)
>> +	if (port->ops && port->ops->dtr_rts)
>>   		port->ops->dtr_rts(port, 1);
>>   }
>>   EXPORT_SYMBOL(tty_port_raise_dtr_rts);
>> @@ -429,7 +429,7 @@ EXPORT_SYMBOL(tty_port_raise_dtr_rts);
>>    */
>>   void tty_port_lower_dtr_rts(struct tty_port *port)
>>   {
>> -	if (port->ops->dtr_rts)
>> +	if (port->ops && port->ops->dtr_rts)
>>   		port->ops->dtr_rts(port, 0);
>>   }
>>   EXPORT_SYMBOL(tty_port_lower_dtr_rts);
>> @@ -684,7 +684,7 @@ int tty_port_open(struct tty_port *port, struct tty_struct *tty,
>>   
>>   	if (!tty_port_initialized(port)) {
>>   		clear_bit(TTY_IO_ERROR, &tty->flags);
>> -		if (port->ops->activate) {
>> +		if (port->ops && port->ops->activate) {
>>   			int retval = port->ops->activate(port, tty);
>>   			if (retval) {
>>   				mutex_unlock(&port->mutex);
>> -- 
>> 2.7.4
>>
> Can you hit this today with any in-kernel drivers?  Or is this only for
> your new code you are adding?
>
> thanks,
>
> greg k-h

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-03-22  8:35 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-03-21 15:43 [PATCH] tty: fix NULL pointer issue when tty_port ops is not set Fabien Dessenne
2019-03-21 17:38 ` Greg Kroah-Hartman
2019-03-22  8:35   ` Fabien DESSENNE

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