RDS: IB: Fix null pointer issue

The id_priv which have a null event_handler setting, is created when call
rdma_create_id function as one step of rds_bind,and then the id_priv will be
destroyed. There is a time window it is attached to the id_list of cma_dev.
At the same time window, fail over got it from list and send perform event
handler.(Porting this fix from UEK2 to UEK3)

Scenario:
1. Port down and do fail over
2. Ap do rds_bind syscall

PID: 47039  TASK: ffff89887e2fe640  CPU: 47  COMMAND: "kworker/u:6"
[exception RIP: unknown or invalid address]
RIP: 0000000000000000  RSP: ffff898e35f15dc8  RFLAGS: 00010282
RAX: 00000000fffffffe  RBX: ffff889b77f6fc00  RCX:ffffffff81c99d88
RDX: 0000000000000000  RSI: ffff896019ee08e8  RDI:ffff889b77f6fc00
RBP: ffff898e35f15df0   R8: ffff896019ee08c8  R9:0000000000000000
R10: 0000000000000400  R11: 0000000000000000  R12:ffff896019ee08c0
R13: ffff889b77f6fe68  R14: ffffffff81c99d80  R15: ffffffffa022a1e0
ORIG_RAX: ffffffffffffffff  CS: 0010 SS: 0018

Orabug: 27843171

Signed-off-by: hui.han <[email protected]>
Signed-off-by: Guanglei Li <[email protected]>
Signed-off-by: Honglei Wang <[email protected]>
Reviewed-by: Junxiao Bi <[email protected]>
Reviewed-by: Yanjun Zhu <[email protected]>
Reviewed-by: Leon Romanovsky <[email protected]>
Acked-by: Santosh Shilimkar <[email protected]>
Acked-by: Doug Ledford <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
(cherry picked from commit 2c0aa08)
Reviewed-by: Håkon Bugge <[email protected]>
Signed-off-by: Brian Maly <[email protected]>

Author: linuxhuihan

net/rds/ib.c

@@ -418,7 +418,8 @@ static int rds_ib_laddr_check(__be32 addr)
 	/* Create a CMA ID and try to bind it. This catches both
 	 * IB and iWARP capable NICs.
 	 */
-	cm_id = rdma_create_id(NULL, NULL, RDMA_PS_TCP, IB_QPT_RC);
+	cm_id = rdma_create_id(rds_rdma_cm_event_handler,
+                               NULL, RDMA_PS_TCP, IB_QPT_RC);
 	if (IS_ERR(cm_id))
 		return -EADDRNOTAVAIL;