[PATCH] net: usbnet: fix a memory leak bug

[PATCH] net: usbnet: fix a memory leak bug

[Wenwen Wang]

In usbnet_start_xmit(), 'urb->sg' is allocated through kmalloc_array() by
invoking build_dma_sg(). Later on, if 'CONFIG_PM' is defined and the if
branch is taken, the execution will go to the label 'deferred'. However,
'urb->sg' is not deallocated on this execution path, leading to a memory
leak bug.

Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
---
 drivers/net/usb/usbnet.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 72514c4..f17fafa 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1433,6 +1433,7 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
 		usb_anchor_urb(urb, &dev->deferred);
 		/* no use to process more packets */
 		netif_stop_queue(net);
+		kfree(urb->sg);
 		usb_put_urb(urb);
 		spin_unlock_irqrestore(&dev->txq.lock, flags);
 		netdev_dbg(dev->net, "Delaying transmission for resumption\n");
-- 
2.7.4

Re: [PATCH] net: usbnet: fix a memory leak bug

[Jack Pham]

On Wed, Aug 14, 2019 at 12:41:33PM -0500, Wenwen Wang wrote:
> In usbnet_start_xmit(), 'urb->sg' is allocated through kmalloc_array() by
> invoking build_dma_sg(). Later on, if 'CONFIG_PM' is defined and the if
> branch is taken, the execution will go to the label 'deferred'. However,
> 'urb->sg' is not deallocated on this execution path, leading to a memory
> leak bug.
> 
> Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
> ---
>  drivers/net/usb/usbnet.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
> index 72514c4..f17fafa 100644
> --- a/drivers/net/usb/usbnet.c
> +++ b/drivers/net/usb/usbnet.c
> @@ -1433,6 +1433,7 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
>  		usb_anchor_urb(urb, &dev->deferred);
>  		/* no use to process more packets */
>  		netif_stop_queue(net);
> +		kfree(urb->sg);
>  		usb_put_urb(urb);

The URB itself is not getting freed here; it is merely added to the
anchor list and will be submitted later upon usbnet_resume(). Therefore
freeing the SG list is premature and incorrect, as it will get freed in
either the tx_complete/tx_done path or upon URB submission failure.

>  		spin_unlock_irqrestore(&dev->txq.lock, flags);
>  		netdev_dbg(dev->net, "Delaying transmission for resumption\n");

Jack
-- 
The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH] net: usbnet: fix a memory leak bug

[Oliver Neukum]

Am Mittwoch, den 14.08.2019, 12:41 -0500 schrieb Wenwen Wang:
> In usbnet_start_xmit(), 'urb->sg' is allocated through kmalloc_array() by
> invoking build_dma_sg(). Later on, if 'CONFIG_PM' is defined and the if
> branch is taken, the execution will go to the label 'deferred'. However,
> 'urb->sg' is not deallocated on this execution path, leading to a memory
> leak bug.

Just to make this clear:

> Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
NACK

For the reason Jack explained. Deferral is not a failure.

	Regards
		Oliver