syn_data was allocated by sk_stream_alloc_skb(), meaning
its destructor and _skb_refdst fields are mangled.
We need to call tcp_skb_tsorted_anchor_cleanup() before
calling kfree_skb() or kernel crashes.
Bug was reported by syzkaller bot.
Fixes: e2080072ed2d ("tcp: new list for sent but unacked skbs for RACK recovery") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Acked-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>