[v2,net] net: hso: check for allocation failure in hso_create_bulk_serial_device()

Message ID YJ6IMH7jI9QFdGIX@mwanda
State New
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  • [v2,net] net: hso: check for allocation failure in hso_create_bulk_serial_device()
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Commit Message

Dan Carpenter May 14, 2021, 2:24 p.m.
In current kernels, small allocations never actually fail so this
patch shouldn't affect runtime.

Originally this error handling code written with the idea that if
the "serial->tiocmget" allocation failed, then we would continue
operating instead of bailing out early.  But in later years we added
an unchecked dereference on the next line.

	serial->tiocmget->serial_state_notification = kzalloc();
        ^^^^^^^^^^^^^^^^^^

Since these allocations are never going fail in real life, this is
mostly a philosophical debate, but I think bailing out early is the
correct behavior that the user would want.  And generally it's safer to
bail as soon an error happens.

Fixes: af0de1303c4e ("usb: hso: obey DMA rules in tiocmget")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v2: Do more extensive clean up.  As Johan pointed out the comments and
later NULL checks can be removed.

 drivers/net/usb/hso.c | 37 ++++++++++++++++++-------------------
 1 file changed, 18 insertions(+), 19 deletions(-)

Comments

Johan Hovold May 17, 2021, 8:07 a.m. | #1
On Fri, May 14, 2021 at 05:24:48PM +0300, Dan Carpenter wrote:
> In current kernels, small allocations never actually fail so this

> patch shouldn't affect runtime.

> 

> Originally this error handling code written with the idea that if

> the "serial->tiocmget" allocation failed, then we would continue

> operating instead of bailing out early.  But in later years we added

> an unchecked dereference on the next line.

> 

> 	serial->tiocmget->serial_state_notification = kzalloc();

>         ^^^^^^^^^^^^^^^^^^

> 

> Since these allocations are never going fail in real life, this is

> mostly a philosophical debate, but I think bailing out early is the

> correct behavior that the user would want.  And generally it's safer to

> bail as soon an error happens.

> 

> Fixes: af0de1303c4e ("usb: hso: obey DMA rules in tiocmget")

> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

> ---

> v2: Do more extensive clean up.  As Johan pointed out the comments and

> later NULL checks can be removed.

> 

>  drivers/net/usb/hso.c | 37 ++++++++++++++++++-------------------

>  1 file changed, 18 insertions(+), 19 deletions(-)

> 

> diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c

> index 3ef4b2841402..260f850d69eb 100644

> --- a/drivers/net/usb/hso.c

> +++ b/drivers/net/usb/hso.c

> @@ -2618,29 +2618,28 @@ static struct hso_device *hso_create_bulk_serial_device(

>  		num_urbs = 2;

>  		serial->tiocmget = kzalloc(sizeof(struct hso_tiocmget),

>  					   GFP_KERNEL);

> +		if (!serial->tiocmget)

> +			goto exit;

>  		serial->tiocmget->serial_state_notification

>  			= kzalloc(sizeof(struct hso_serial_state_notification),

>  					   GFP_KERNEL);

> -		/* it isn't going to break our heart if serial->tiocmget

> -		 *  allocation fails don't bother checking this.

> -		 */

> -		if (serial->tiocmget && serial->tiocmget->serial_state_notification) {

> -			tiocmget = serial->tiocmget;

> -			tiocmget->endp = hso_get_ep(interface,

> -						    USB_ENDPOINT_XFER_INT,

> -						    USB_DIR_IN);

> -			if (!tiocmget->endp) {

> -				dev_err(&interface->dev, "Failed to find INT IN ep\n");

> -				goto exit;

> -			}

> -

> -			tiocmget->urb = usb_alloc_urb(0, GFP_KERNEL);

> -			if (tiocmget->urb) {

> -				mutex_init(&tiocmget->mutex);

> -				init_waitqueue_head(&tiocmget->waitq);

> -			} else

> -				hso_free_tiomget(serial);

> +		if (!serial->tiocmget->serial_state_notification)

> +			goto exit;

> +		tiocmget = serial->tiocmget;

> +		tiocmget->endp = hso_get_ep(interface,

> +					    USB_ENDPOINT_XFER_INT,

> +					    USB_DIR_IN);

> +		if (!tiocmget->endp) {

> +			dev_err(&interface->dev, "Failed to find INT IN ep\n");

> +			goto exit;

>  		}

> +

> +		tiocmget->urb = usb_alloc_urb(0, GFP_KERNEL);

> +		if (tiocmget->urb) {

> +			mutex_init(&tiocmget->mutex);

> +			init_waitqueue_head(&tiocmget->waitq);

> +		} else

> +			hso_free_tiomget(serial);


This should probably be changed to bail out on allocation errors as well
now but that can be done as a follow-up. Either way:

Reviewed-by: Johan Hovold <johan@kernel.org>


>  	}

>  	else

>  		num_urbs = 1;


Johan
patchwork-bot+netdevbpf@kernel.org May 17, 2021, 9 p.m. | #2
Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Fri, 14 May 2021 17:24:48 +0300 you wrote:
> In current kernels, small allocations never actually fail so this
> patch shouldn't affect runtime.
> 
> Originally this error handling code written with the idea that if
> the "serial->tiocmget" allocation failed, then we would continue
> operating instead of bailing out early.  But in later years we added
> an unchecked dereference on the next line.
> 
> [...]

Here is the summary with links:
  - [v2,net] net: hso: check for allocation failure in hso_create_bulk_serial_device()
    https://git.kernel.org/netdev/net/c/31db0dbd7244

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Patch

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index 3ef4b2841402..260f850d69eb 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -2618,29 +2618,28 @@  static struct hso_device *hso_create_bulk_serial_device(
 		num_urbs = 2;
 		serial->tiocmget = kzalloc(sizeof(struct hso_tiocmget),
 					   GFP_KERNEL);
+		if (!serial->tiocmget)
+			goto exit;
 		serial->tiocmget->serial_state_notification
 			= kzalloc(sizeof(struct hso_serial_state_notification),
 					   GFP_KERNEL);
-		/* it isn't going to break our heart if serial->tiocmget
-		 *  allocation fails don't bother checking this.
-		 */
-		if (serial->tiocmget && serial->tiocmget->serial_state_notification) {
-			tiocmget = serial->tiocmget;
-			tiocmget->endp = hso_get_ep(interface,
-						    USB_ENDPOINT_XFER_INT,
-						    USB_DIR_IN);
-			if (!tiocmget->endp) {
-				dev_err(&interface->dev, "Failed to find INT IN ep\n");
-				goto exit;
-			}
-
-			tiocmget->urb = usb_alloc_urb(0, GFP_KERNEL);
-			if (tiocmget->urb) {
-				mutex_init(&tiocmget->mutex);
-				init_waitqueue_head(&tiocmget->waitq);
-			} else
-				hso_free_tiomget(serial);
+		if (!serial->tiocmget->serial_state_notification)
+			goto exit;
+		tiocmget = serial->tiocmget;
+		tiocmget->endp = hso_get_ep(interface,
+					    USB_ENDPOINT_XFER_INT,
+					    USB_DIR_IN);
+		if (!tiocmget->endp) {
+			dev_err(&interface->dev, "Failed to find INT IN ep\n");
+			goto exit;
 		}
+
+		tiocmget->urb = usb_alloc_urb(0, GFP_KERNEL);
+		if (tiocmget->urb) {
+			mutex_init(&tiocmget->mutex);
+			init_waitqueue_head(&tiocmget->waitq);
+		} else
+			hso_free_tiomget(serial);
 	}
 	else
 		num_urbs = 1;