kernel: tipc: Fix use-after-free in tipc_conn_close()

In the Linux kernel, the following vulnerability has been resolved: tipc: Fix use-after-free in tipcconnclose. syzbot reported a null-ptr-deref in tipcconnclose during netns dismantle. 0 tipctopsrvstop iterates tipcnetnet-topsrv-connidr and calls tipcconnclose for each tipcconn. The problem is th...