usbip: vudc: fix null pointer dereference on udc->lock

BugLink: http://bugs.launchpad.net/bugs/1756978
commit df3334c223a033f562645712e832ca4cbb326bbf upstream.

Currently the driver attempts to spin lock on udc->lock before a NULL
pointer check is performed on udc, hence there is a potential null
pointer dereference on udc->lock.  Fix this by moving the null check
on udc before the lock occurs.

Fixes: ea6873a45a22 ("usbip: vudc: Add SysFS infrastructure for VUDC")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Shuah Khan <shuahkh@osg.samsung.com>
Reviewed-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/drivers/usb/usbip/vudc_sysfs.c b/drivers/usb/usbip/vudc_sysfs.c
index 1adc8af292ece241515c49b784cd65b2432e81b8..59a4d1bcda1ed2f4d3e0e55529ece679d108db86 100644 (file)
--- a/drivers/usb/usbip/vudc_sysfs.c
+++ b/drivers/usb/usbip/vudc_sysfs.c
@@ -105,10 +105,14 @@ static ssize_t store_sockfd(struct device *dev, struct device_attribute *attr,
        if (rv != 0)
                return -EINVAL;
 
+       if (!udc) {
+               dev_err(dev, "no device");
+               return -ENODEV;
+       }
        spin_lock_irqsave(&udc->lock, flags);
        /* Don't export what we don't have */
-       if (!udc || !udc->driver || !udc->pullup) {
-               dev_err(dev, "no device or gadget not bound");
+       if (!udc->driver || !udc->pullup) {
+               dev_err(dev, "gadget not bound");
                ret = -ENODEV;
                goto unlock;
        }