[RFT] lan78xx: FIX use-after-free in lan78xx_write_reg

[Arvind Yadav]

We are not releasing 'buf' memory on failure or disconnect a device.

Adding 'u8 *buf' as part of 'lan78xx_net' structure to make proper
handle for 'buf'.
Now releasing 'buf' memory on failure. It's allocate first in
lan78xx_probe() and it should be freed last in lan78xx_disconnect().

Signed-off-by: Arvind Yadav <arvind.yadav...@gmail.com>
---
 drivers/net/usb/lan78xx.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index b99a7fb..e653982 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -402,6 +402,7 @@ struct lan78xx_net {
        struct statstage        stats;
 
        struct irq_domain_data  domain_data;
+       u8 *buf;
 };
 
 /* define external phy id */
@@ -3470,6 +3471,9 @@ static void lan78xx_disconnect(struct usb_interface *intf)
 
        usb_scuttle_anchored_urbs(&dev->deferred);
 
+       kfree(dev->buf);
+       dev->buf = NULL;
+
        lan78xx_unbind(dev, intf);
 
        usb_kill_urb(dev->urb_intr);
@@ -3520,7 +3524,6 @@ static int lan78xx_probe(struct usb_interface *intf,
        int ret;
        unsigned maxp;
        unsigned period;
-       u8 *buf = NULL;
 
        udev = interface_to_usbdev(intf);
        udev = usb_get_dev(udev);
@@ -3588,16 +3591,15 @@ static int lan78xx_probe(struct usb_interface *intf,
        period = dev->ep_intr->desc.bInterval;
 
        maxp = usb_maxpacket(dev->udev, dev->pipe_intr, 0);
-       buf = kmalloc(maxp, GFP_KERNEL);
-       if (buf) {
+       dev->buf = kmalloc(maxp, GFP_KERNEL);
+       if (dev->buf) {
                dev->urb_intr = usb_alloc_urb(0, GFP_KERNEL);
                if (!dev->urb_intr) {
                        ret = -ENOMEM;
-                       kfree(buf);
                        goto out3;
                } else {
                        usb_fill_int_urb(dev->urb_intr, dev->udev,
-                                        dev->pipe_intr, buf, maxp,
+                                        dev->pipe_intr, dev->buf, maxp,
                                         intr_complete, dev, period);
                }
        }
@@ -3626,6 +3628,8 @@ static int lan78xx_probe(struct usb_interface *intf,
        return 0;
 
 out3:
+       kfree(dev->buf);
+       dev->buf = NULL;
        lan78xx_unbind(dev, intf);
 out2:
        free_netdev(netdev);
-- 
1.9.1