The patch series fixes a possible racy use-after-free scenario described in 2/2: if j1939_can_rx_register() fails then the concurrent thread may have already read the invalid priv structure. The 1/2 makes j1939_netdev_lock a mutex so that access to j1939_can_rx_register() can be serialized without changing GFP_KERNEL to GFP_ATOMIC inside can_rx_register(). This seems to be safe. Note that the patch series has been tested only via Syzkaller and not with a real device.
