igb: release already assigned MSI-X interrupts if setup fails

During MSI-X setup the system might run out of vectors. If this happens the
already assigned vectors for this NIC should be freed before trying the
disable MSI-X. Failing to do so results in the following oops.

kernel BUG at drivers/pci/msi.c:341!
[...]
Call Trace:
 [<ffffffff8128f39d>] pci_disable_msix+0x3d/0x60
 [<ffffffffa037d1ce>] igb_reset_interrupt_capability+0x27/0x5c [igb]
 [<ffffffffa037d229>] igb_clear_interrupt_scheme+0x26/0x2d [igb]
 [<ffffffffa0384268>] igb_request_irq+0x73/0x297 [igb]
 [<ffffffffa0384554>] __igb_open+0xc8/0x223 [igb]
 [<ffffffffa0384815>] igb_open+0x13/0x15 [igb]
 [<ffffffff8144592f>] __dev_open+0xbf/0x120
 [<ffffffff81443e51>] __dev_change_flags+0xa1/0x180
 [<ffffffff81445828>] dev_change_flags+0x28/0x70
 [<ffffffff814af537>] devinet_ioctl+0x5b7/0x620
 [<ffffffff814b01c8>] inet_ioctl+0x88/0xa0
 [<ffffffff8142e8a0>] sock_do_ioctl+0x30/0x70
 [<ffffffff8142ecf2>] sock_ioctl+0x72/0x270
 [<ffffffff8118062c>] do_vfs_ioctl+0x8c/0x340
 [<ffffffff81180981>] sys_ioctl+0xa1/0xb0
 [<ffffffff815161a9>] system_call_fastpath+0x16/0x1b
Code: 48 89 df e8 1f 40 ed ff 4d 39 e6 49 8b 45 10 75 b6 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f c9 c3 48 8b 7b 20 e8 3e 91 db ff eb ae <0f> 0b eb fe 0f 1f 84 00 00 00 00 00 55 48 89 e5 0f 1f 44 00 00
RIP  [<ffffffff8128e144>] free_msi_irqs+0x124/0x130
 RSP <ffff880037503bd8>

Signed-off-by: Stefan Assmann <sassmann@kpanic.de>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igb/igb_main.c

@@ -832,17 +832,18 @@ static int igb_request_msix(struct igb_adapter *adapter)
 {
 	struct net_device *netdev = adapter->netdev;
 	struct e1000_hw *hw = &adapter->hw;
-	int i, err = 0, vector = 0;
+	int i, err = 0, vector = 0, free_vector = 0;
 
 	err = request_irq(adapter->msix_entries[vector].vector,
 	                  igb_msix_other, 0, netdev->name, adapter);
 	if (err)
-		goto out;
-	vector++;
+		goto err_out;
 
 	for (i = 0; i < adapter->num_q_vectors; i++) {
 		struct igb_q_vector *q_vector = adapter->q_vector[i];
 
+		vector++;
+
 		q_vector->itr_register = hw->hw_addr + E1000_EITR(vector);
 
 		if (q_vector->rx.ring && q_vector->tx.ring)
@@ -861,13 +862,22 @@ static int igb_request_msix(struct igb_adapter *adapter)
 		                  igb_msix_ring, 0, q_vector->name,
 		                  q_vector);
 		if (err)
-			goto out;
-		vector++;
+			goto err_free;
 	}
 
 	igb_configure_msix(adapter);
 	return 0;
-out:
+
+err_free:
+	/* free already assigned IRQs */
+	free_irq(adapter->msix_entries[free_vector++].vector, adapter);
+
+	vector--;
+	for (i = 0; i < vector; i++) {
+		free_irq(adapter->msix_entries[free_vector++].vector,
+			 adapter->q_vector[i]);
+	}
+err_out:
 	return err;
 }