[PATCH] ixgbe: fix crashing with ixgbe_vlan_filter_enable

[Yinghai Lu <yinghai@kernel.org>]

happens with reboot or call kexec on system with ixgbe.

[ 4912.773390] BUG: unable to handle kernel NULL pointer dereference
[ 4912.785756] IP: [<ffffffff81691600>] ixgbe_vlan_filter_enable+0x74/0xda
[ 4912.794084] PGD 10391a0067 PUD 1022e3c067 PMD 0
[ 4912.805976] Oops: 0000 [#1] SMP
[ 4912.809312] last sysfs file: /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/host4/target4:2:0/4:2:0:0/vendor
[ 4912.828965] CPU 1
[ 4912.830533] Modules linked in:
[ 4912.834366]
[ 4912.835288] Pid: 25366, comm: reboot Not tainted 2.6.34-rc4-tip-yh-04420-g4537151-dirty #70      
[ 4912.854250] RIP: 0010:[<ffffffff81691600>]  [<ffffffff81691600>] ixgbe_vlan_filter_enable+0x74/0xda
[ 4912.870439] RSP: 0018:ffff88203de49d08  EFLAGS: 00010287
[ 4912.885521] RAX: 0000000000000000 RBX: ffff88703d5d8900 RCX: ffff88703d5d8900
[ 4912.896225] RDX: 0000000000000000 RSI: 0000000000000040 RDI: ffff88703d5d8900
[ 4912.908265] RBP: ffff88203de49d08 R08: ffffc90047280000 R09: ffff88203de49b98
[ 4912.915174] R10: 0000000000000000 R11: ffff88203de49d38 R12: ffff88703d5d8000
[ 4912.936333] R13: ffff88703d5d9e80 R14: 0000000000000000 R15: 0000000000000000
[ 4912.947284] FS:  00007f91db5a36f0(0000) GS:ffff880079e00000(0000) knlGS:0000000000000000
[ 4912.965019] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 4912.970282] CR2: 000000000000002e CR3: 0000001021d27000 CR4: 00000000000006e0
[ 4912.986573] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 4912.997240] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 4913.012609] Process reboot (pid: 25366, threadinfo ffff88203de48000, task ffff88203d902340)
[ 4913.028237] Stack:
[ 4913.030121]  ffff88203de49d38 ffffffff81697d16 ffff88703d5d8900 ffff88503ed00000
[ 4913.045165] <0> 000000000000001e ffff88703d5d8000 ffff88203de49d98 ffffffff81697e46
[ 4913.053297] <0> ffff88203d902340 ffffffff81bd9fc4 ffff88203de49db7 0000000000000000
[ 4913.070554] Call Trace:
[ 4913.074948]  [<ffffffff81697d16>] ixgbe_set_rx_mode+0x137/0x17e
[ 4913.086386]  [<ffffffff81697e46>] __ixgbe_shutdown+0xe9/0x1a6
[ 4913.092895]  [<ffffffff81bd9fc4>] ? _raw_spin_unlock_irq+0x30/0x36
[ 4913.108970]  [<ffffffff81697f1d>] ixgbe_shutdown+0x1a/0x43
[ 4913.113514]  [<ffffffff813e3bea>] pci_device_shutdown+0x2c/0x40
[ 4913.128080]  [<ffffffff81489e25>] device_shutdown+0x53/0x74
[ 4913.135736]  [<ffffffff8108dd91>] kernel_restart_prepare+0x2c/0x33
[ 4913.147206]  [<ffffffff8108dddb>] kernel_restart+0x16/0x48
[ 4913.154807]  [<ffffffff8108df6f>] sys_reboot+0x150/0x196
[ 4913.167525]  [<ffffffff810a4891>] ? trace_hardirqs_on+0xd/0xf
[ 4913.175020]  [<ffffffff811430c2>] ? mntput_no_expire+0x2c/0xf5
[ 4913.191952]  [<ffffffff8112da8c>] ? __fput+0x1d8/0x1e7
[ 4913.197452]  [<ffffffff81033b8c>] ? sysret_check+0x27/0x62
[ 4913.207708]  [<ffffffff81bd9472>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[ 4913.212377]  [<ffffffff81033b5b>] system_call_fastpath+0x16/0x1b
[ 4913.230877] Code: 00 00 00 40 48 8b 97 80 15 00 00 25 ff ff ff df 89 82 88 50 00 00 31 d2 48 89 f9 eb 6a 48 8b 81 40 0e 00 00 4c 8b 87 80 15 00 00 <0f> b7 40 2e 83 f8 3f 7f 0d 89 c6 c1 e6 06 81 c6 28 10 00 00 eb
[ 4913.268163] RIP  [<ffffffff81691600>] ixgbe_vlan_filter_enable+0x74/0xda
[ 4913.273435]  RSP <ffff88203de49d08>
[ 4913.285451] CR2: 000000000000002e
[ 4913.290668] ---[ end trace 0aaa048b0b730b65 ]---

add checking before reference them.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 drivers/net/ixgbe/ixgbe_main.c |   16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

Index: linux-2.6/drivers/net/ixgbe/ixgbe_main.c
===================================================================
--- linux-2.6.orig/drivers/net/ixgbe/ixgbe_main.c
+++ linux-2.6/drivers/net/ixgbe/ixgbe_main.c
@@ -2915,7 +2915,13 @@ static void ixgbe_vlan_filter_disable(st
 			break;
 #endif
 		for (i = 0; i < adapter->num_rx_queues; i++) {
-			j = adapter->rx_ring[i]->reg_idx;
+			struct ixgbe_ring *rx_ring;
+
+			rx_ring = adapter->rx_ring[i];
+			if (!rx_ring)
+				continue;
+
+			j = rx_ring->reg_idx;
 			vlnctrl = IXGBE_READ_REG(hw, IXGBE_RXDCTL(j));
 			vlnctrl &= ~IXGBE_RXDCTL_VME;
 			IXGBE_WRITE_REG(hw, IXGBE_RXDCTL(j), vlnctrl);
@@ -2947,7 +2953,13 @@ static void ixgbe_vlan_filter_enable(str
 		vlnctrl &= ~IXGBE_VLNCTRL_CFIEN;
 		IXGBE_WRITE_REG(hw, IXGBE_VLNCTRL, vlnctrl);
 		for (i = 0; i < adapter->num_rx_queues; i++) {
-			j = adapter->rx_ring[i]->reg_idx;
+			struct ixgbe_ring *rx_ring;
+
+			rx_ring = adapter->rx_ring[i];
+			if (!rx_ring)
+				continue;
+
+			j = rx_ring->reg_idx;
 			vlnctrl = IXGBE_READ_REG(hw, IXGBE_RXDCTL(j));
 			vlnctrl |= IXGBE_RXDCTL_VME;
 			IXGBE_WRITE_REG(hw, IXGBE_RXDCTL(j), vlnctrl);