usb: gadget: NCM: Protect dev->port_usb using dev->lock

This commit incorporates findings from
https://lkml.org/lkml/2016/4/25/594

The function has been modified to make sure we hold
the dev lock when accessing the net device pointer.

Acked-by: Jim Baxter <jim_baxter@mentor.com>
Signed-off-by: Harish Jenny K N <harish_kandiga@mentor.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index 9c8c9ed..8cb0803 100644 (file)
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -553,14 +553,16 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
                spin_lock_irqsave(&dev->lock, flags);
                if (dev->port_usb)
                        skb = dev->wrap(dev->port_usb, skb);
-               spin_unlock_irqrestore(&dev->lock, flags);
                if (!skb) {
                        /* Multi frame CDC protocols may store the frame for
                         * later which is not a dropped frame.
                         */
                        if (dev->port_usb &&
-                                       dev->port_usb->supports_multi_frame)
+                                       dev->port_usb->supports_multi_frame) {
+                               spin_unlock_irqrestore(&dev->lock, flags);
                                goto multiframe;
+                       }
+                       spin_unlock_irqrestore(&dev->lock, flags);
                        goto drop;
                }
        }
@@ -578,6 +580,7 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
                req->zero = 0;
        else
                req->zero = 1;
+       spin_unlock_irqrestore(&dev->lock, flags);
 
        /* use zlp framing on tx for strict CDC-Ether conformance,
         * though any robust network rx path ignores extra padding.