In the Linux kernel, the following vulnerability has been resolved:
ipv6: ioam: fix potential NULL dereferences in _ioam6filltracedata()
We need to check __in6devget() for possible NULL value, as suggested by Yiming Qian.
Also add skbdstdevrcu() instead of skbdstdev(), and two missing READONCE().
Note that @dev can't be NULL.