tipc: protect node reset trace dump with node lock

In the Linux kernel, the following vulnerability has been resolved: tipc: protect node reset trace dump with node lock The tipc_node_reset_links trace event asks tipc_node_dump() to walk the node's link entries. Unlike the other node events that request link data, this event runs without the node lock. This permits bearer teardown to free a link while the trace callback is dumping it: CPU 0 CPU 1 trace_tipc_node_reset_links() tipc_node_dump() l = n->links[0].link tipc_node_write_lock() kfree(l) n->links[0].link = NULL tipc_node_write_unlock() tipc_link_dump(l) tipc_link_dump() then dereferences the stale pointer. KASAN reported: BUG: KASAN: slab-use-after-free in tipc_link_dump Read of size 4 by task poc/115 Call Trace: tipc_link_dump+0x10cb/0x16b0 tipc_node_dump+0x4bb/0x740 trace_event_raw_event_tipc_node_class+0x258/0x360 tipc_node_reset_links+0x14d/0x1a0 tipc_rcv+0x13f5/0x3030 tipc_udp_recv+0x4e3/0x670 Allocated by task 0: tipc_link_create+0x1e1/0x1020 tipc_node_check_dest+0x7d2/0x11a0 tipc_disc_rcv+0xdbf/0x1430 Freed by task 89: kfree+0x131/0x3c0 tipc_node_link_down+0x267/0x4b0 tipc_node_delete_links+0xec/0x160 bearer_disable+0x107/0x260 Take the node write lock around the trace event. This serializes the dump against tipc_node_link_down(delete=true), which frees the link under the same write lock.