HID: hiddev: fix memory corruption due to invalid intfdata

Commit bd25f4dd6972755579d0 ("HID: hiddev: use usb_find_interface,
get rid of BKL") introduced using of private intfdata in hiddev for
purpose of storing hiddev pointer.

This is a problem, because intf pointer is already being set to struct
hid_device pointer by HID core. This obviously lead to memory corruptions
at device disconnect time, such as

WARNING: at lib/kobject.c:595 kobject_put+0x37/0x4b()
kobject: '(null)' (ffff88011e9cd898): is not initialized, yet kobject_put() is being called.

Convert hiddev into accessing hiddev through struct hid_device which is
in intfdata already.

Reported-and-tested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Reported-and-tested-by: Heinz Diehl <htd@fritha.org>
Reported-and-tested-by: Alan Ott <alan@signal11.us>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
index f2850171a69b..0a29c51114aa 100644
--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -266,13 +266,15 @@ static int hiddev_open(struct inode *inode, struct file *file)
 {
         struct hiddev_list *list;
         struct usb_interface *intf;
+        struct hid_device *hid;
         struct hiddev *hiddev;
         int res;
 
         intf = usb_find_interface(&hiddev_driver, iminor(inode));
         if (!intf)
                 return -ENODEV;
-        hiddev = usb_get_intfdata(intf);
+        hid = usb_get_intfdata(intf);
+        hiddev = hid->hiddev;
 
         if (!(list = kzalloc(sizeof(struct hiddev_list), GFP_KERNEL)))
                 return -ENOMEM;
@@ -890,7 +892,6 @@ int hiddev_connect(struct hid_device *hid, unsigned int force)
         hid->hiddev = hiddev;
         hiddev->hid = hid;
         hiddev->exist = 1;
-        usb_set_intfdata(usbhid->intf, usbhid);
         retval = usb_register_dev(usbhid->intf, &hiddev_class);
         if (retval) {
                 err_hid("Not able to get a minor for this device.");