One of our users reports consistently hitting a NULL dereference that resolves to the "hid_to_usb_dev(hid);" call in hiddev_ioctl(), when disconnecting a Lego WeDo USB HID device from an OLPC XO running Scratch software. There's a FIXME comment and a guard against the dereference, but that happens farther down the function than the initial dereference does. This patch moves the call to be below the guard, and the user reports that it fixes the problem for him. OLPC bug report: http://dev.laptop.org/ticket/10174 Signed-off-by: Chris Ball <cjb@xxxxxxxxxx> --- drivers/hid/usbhid/hiddev.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c index c24d2fa..7ec009a 100644 --- a/drivers/hid/usbhid/hiddev.c +++ b/drivers/hid/usbhid/hiddev.c @@ -593,7 +593,7 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg) struct hiddev_list *list = file->private_data; struct hiddev *hiddev = list->hiddev; struct hid_device *hid = hiddev->hid; - struct usb_device *dev = hid_to_usb_dev(hid); + struct usb_device *dev; struct hiddev_collection_info cinfo; struct hiddev_report_info rinfo; struct hiddev_field_info finfo; @@ -607,9 +607,11 @@ static long hiddev_ioctl(struct file *file, unsigned int cmd, unsigned long arg) /* Called without BKL by compat methods so no BKL taken */ /* FIXME: Who or what stop this racing with a disconnect ?? */ - if (!hiddev->exist) + if (!hiddev->exist || !hid) return -EIO; + dev = hid_to_usb_dev(hid); + switch (cmd) { case HIDIOCGVERSION: -- 1.7.0.1 -- Chris Ball <cjb@xxxxxxxxxx> One Laptop Per Child -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
