On Fri, Dec 03, 2010 at 08:27:46PM +0300, Valentine Barshak wrote: > A USB HID device can be disconnected at any time. > If this happens right before or while hiddev_ioctl is in progress, > the hiddev_ioctl tries to access invalid hiddev->hid pointer. > When the hid device is disconnected, the hiddev_disconnect() > ends up with a call to hid_device_release() which frees > hid_device, but doesn't set the hiddev->hid pointer to NULL. > If the deallocated memory region has been re-used by the kernel, > this can cause a crash or memory corruption. > > Since disconnect can happen at any time, we can't initialize > struct hid_device *hid = hiddev->hid at the beginning of ioctl > and then use it. > > This change checks hiddev->exist flag while holding > the existancelock and uses hid_device only if it exists. Why didn't you take the lock and check hiddev->exist at the beginning of ioctl handler instead of pushing it down into individual command handlers? I guess it would slow down HIDIOCGVERSION but I think we could pay this price for code that is more clear ;) -- Dmitry -- 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
