[PATCH 3/3] ehea: do not dereference possible NULL port

[Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>]

port may be NULL when we receive an interrupt too early in the probe.

commit 8c4877a4128e7931077b024a891a4b284d8756a3, in particular, has
introduced this problem in the case of port state change interrupt.

This causes crashes in some situations:

[c000000f7ff7fd60] d000000008e223f0 .ehea_neq_tasklet+0x78/0x148 [ehea]
[c000000f7ff7fe00] c0000000000b6cac .tasklet_hi_action+0xdc/0x210
[c000000f7ff7fea0] c0000000000b7cc8 .__do_softirq+0x178/0x300
[c000000f7ff7ff90] c000000000022694 .call_do_softirq+0x14/0x24
[c000000f68ee7900] c000000000010e04 .do_softirq+0xec/0x110
[c000000f68ee79a0] c0000000000b789c .irq_exit+0xac/0xe0
[c000000f68ee7a20] c0000000000110bc .do_IRQ+0x114/0x2a8
[c000000f68ee7ae0] c00000000000553c hardware_interrupt_entry+0x18/0x1c
--- Exception: 501 (Hardware Interrupt) at c00000000000e6bc
.arch_local_irq_rest
ore+0x34/0x48
[link register   ] c000000000017a7c .cpu_idle+0x194/0x2f8
[c000000f68ee7dd0] c000000000017a70 .cpu_idle+0x188/0x2f8 (unreliable)
[c000000f68ee7e90] c00000000066b264 .start_secondary+0x3e4/0x524
[c000000f68ee7f90] c0000000000092e8 .start_secondary_prolog+0x10/0x14

cpu 0x8: Vector: 300 (Data Access) at [c000000f7ff7fa40]
    pc: d000000008e21fac: .ehea_parse_eqe+0x6c/0x438 [ehea]
    lr: d000000008e223f0: .ehea_neq_tasklet+0x78/0x148 [ehea]
    sp: c000000f7ff7fcc0
   msr: 8000000000009032
   dar: 8
 dsisr: 40000000
  current = 0xc000000f68efc0c0
  paca    = 0xc00000000ff41800
    pid   = 0, comm = kworker/0:1

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Cc: Joe Perches <joe@perches.com>
---
 drivers/net/ethernet/ibm/ehea/ehea_main.c |   13 +++++++------
 1 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ehea/ehea_main.c b/drivers/net/ethernet/ibm/ehea/ehea_main.c
index 35caeb5..5e64e66 100644
--- a/drivers/net/ethernet/ibm/ehea/ehea_main.c
+++ b/drivers/net/ethernet/ibm/ehea/ehea_main.c
@@ -1156,21 +1156,22 @@ static void ehea_parse_eqe(struct ehea_adapter *adapter, u64 eqe)
 	u8 ec;
 	u8 portnum;
 	struct ehea_port *port;
-	struct net_device *dev;
+	struct net_device *dev = NULL;
 
 	ec = EHEA_BMASK_GET(NEQE_EVENT_CODE, eqe);
 	portnum = EHEA_BMASK_GET(NEQE_PORTNUM, eqe);
 	port = ehea_get_port(adapter, portnum);
+	if (!port) {
+		pr_err("%s: unknown portnum %d, event %x\n",
+					adapter->ofdev->name, portnum, ec);
+		return;
+	}
+
 	dev = port->netdev;
 
 	switch (ec) {
 	case EHEA_EC_PORTSTATE_CHG:	/* port state change */
 
-		if (!port) {
-			netdev_err(dev, "unknown portnum %x\n", portnum);
-			break;
-		}
-
 		if (EHEA_BMASK_GET(NEQE_PORT_UP, eqe)) {
 			if (!netif_carrier_ok(dev)) {
 				ret = ehea_sense_port_attr(port);
-- 
1.7.4.4