CVE-2024-56645: Undefined Security Weakness

In the Linux kernel, the following vulnerability has been resolved:

can: j1939: j1939_session_new(): fix skb reference counting

Since j1939_session_skb_queue() does an extra skb_get() for each new skb, do the same for the initial one in j1939_session_new() to avoid refcount underflow.

[mkl: clean up commit message]