net/llc: avoid BUG_ON() in skb_orphan()

net/llc: avoid BUG_ON() in skb_orphan()

It seems nobody used LLC since linux-3.12.

Fortunately fuzzers like syzkaller still know how to run this code,
otherwise it would be no fun.

Setting skb->sk without skb->destructor leads to all kinds of
bugs, we now prefer to be very strict about it.

Ideally here we would use skb_set_owner() but this helper does not exist yet,
only CAN seems to have a private helper for that.

Orabug: 25802599
CVE: CVE-2017-6345

Fixes: 376c7311bdb6 ("net: add a temporary sanity check in skb_orphan()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Aniket Alshi <aniket.alshi@oracle.com>
(cherry picked from commit 8b74d439e1697110c5e5c600643e823eb1dd0762)
Reviewed-by: Jack Vogel <jack.vogel@oracle.com>