[PATCH] tipc: ensure skb->lock is initialised

[Chris Packham]

tipc_named_node_up() creates a skb list. It passes the list to
tipc_node_xmit() which has some code paths that can call
skb_queue_purge() which relies on the list->lock being initialised.
Ensure tipc_named_node_up() uses skb_queue_head_init() so that the lock
is explicitly initialised.

Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>
---

I'm updating our products to use the latest kernel. One change that we have that
doesn't appear to have been upstreamed is related to the following soft lockup.

NMI watchdog: BUG: soft lockup - CPU#3 stuck for 23s! [swapper/3:0]
Modules linked in: tipc jitterentropy_rng echainiv drbg platform_driver(O) ipifwd(PO)
CPU: 3 PID: 0 Comm: swapper/3 Tainted: P           O    4.4.6-at1 #1
task: a3054e00 ti: ac6b4000 task.ti: a307a000
NIP: 806891c4 LR: 804f5060 CTR: 804f50d0
REGS: ac6b59b0 TRAP: 0901   Tainted: P           O     (4.4.6-at1)
MSR: 00029002 <CE,EE,ME>  CR: 84002088  XER: 20000000

GPR00: 804f50fc ac6b5a60 a3054e00 00029002 00000101 01001011 00000000 00000001
GPR08: 00021002 c1502d1c ac6b5ae4 00000000 804f50d0
NIP [806891c4] _raw_spin_lock_irqsave+0x44/0x80
LR [804f5060] skb_dequeue+0x20/0x90
Call Trace:
[ac6b5a80] [804f50fc] skb_queue_purge+0x2c/0x50
[ac6b5a90] [c1511058] tipc_node_xmit+0x138/0x170 [tipc]
[ac6b5ad0] [c1509e58] tipc_named_node_up+0x88/0xa0 [tipc]
[ac6b5b00] [c150fc1c] tipc_netlink_compat_stop+0x9bc/0xf50 [tipc]
[ac6b5b20] [c1511638] tipc_rcv+0x418/0x9b0 [tipc]
[ac6b5bc0] [c150218c] tipc_bcast_stop+0xfc/0x7b0 [tipc]
[ac6b5bd0] [80504e38] __netif_receive_skb_core+0x468/0xa10
[ac6b5c70] [805082fc] netif_receive_skb_internal+0x3c/0xe0
[ac6b5ca0] [80642a48] br_handle_frame_finish+0x1d8/0x4d0
[ac6b5d10] [80642f30] br_handle_frame+0x1f0/0x330
[ac6b5d60] [80504ec8] __netif_receive_skb_core+0x4f8/0xa10
[ac6b5e00] [805082fc] netif_receive_skb_internal+0x3c/0xe0
[ac6b5e30] [8044c868] _dpa_rx+0x148/0x5c0
[ac6b5ea0] [8044b0c8] priv_rx_default_dqrr+0x98/0x170
[ac6b5ed0] [804d1338] qman_p_poll_dqrr+0x1b8/0x240
[ac6b5f00] [8044b1c0] dpaa_eth_poll+0x20/0x60
[ac6b5f20] [805087cc] net_rx_action+0x15c/0x320
[ac6b5f80] [8002594c] __do_softirq+0x13c/0x250
[ac6b5fe0] [80025c34] irq_exit+0xb4/0xf0
[ac6b5ff0] [8000d81c] call_do_irq+0x24/0x3c
[a307be60] [80004acc] do_IRQ+0x8c/0x120
[a307be80] [8000f450] ret_from_except+0x0/0x18
--- interrupt: 501 at arch_cpu_idle+0x24/0x70

Eyeballing the code I think it can still happen since tipc_named_node_up
allocates struct sk_buff_head head on the stack so it could have arbitary
content.

 net/tipc/name_distr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/tipc/name_distr.c b/net/tipc/name_distr.c
index 61219f0b9677..44abc8e9c990 100644
--- a/net/tipc/name_distr.c
+++ b/net/tipc/name_distr.c
@@ -190,7 +190,7 @@ void tipc_named_node_up(struct net *net, u32 dnode)
 	struct name_table *nt = tipc_name_table(net);
 	struct sk_buff_head head;
 
-	__skb_queue_head_init(&head);
+	skb_queue_head_init(&head);
 
 	read_lock_bh(&nt->cluster_scope_lock);
 	named_distribute(net, &head, dnode, &nt->cluster_scope);
-- 
2.22.0