kernel: 3.14: backport for igb driver resolving a driver crash

Signed-off-by: Tim Harvey <tharvey@gateworks.com>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42295 3c298f89-4303-0410-b956-a3cf2f4a3e73

target/linux/generic/patches-3.14/780-igb-Fix-Null-pointer-dereference-in-igb_reset_q_vect.patch

@@ -0,0 +1,40 @@
+From cb06d102327eadcd1bdc480bfd9f8876251d1007 Mon Sep 17 00:00:00 2001
+From: Christoph Paasch <christoph.paasch@uclouvain.be>
+Date: Fri, 21 Mar 2014 03:48:19 -0700
+Subject: [PATCH] igb: Fix Null-pointer dereference in igb_reset_q_vector
+
+When igb_set_interrupt_capability() calls
+igb_reset_interrupt_capability() (e.g., because CONFIG_PCI_MSI is unset),
+num_q_vectors has been set but no vector has yet been allocated.
+
+igb_reset_interrupt_capability() will then call igb_reset_q_vector,
+which assumes that the vector is allocated. As this is not the case, we
+are accessing a NULL-pointer.
+
+This patch fixes it by checking that q_vector is indeed different from
+NULL.
+
+Fixes: 02ef6e1d0b0023 (igb: Fix queue allocation method to accommodate changing during runtime)
+Cc: Carolyn Wyborny <carolyn.wyborny@intel.com>
+Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
+Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
+Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
+---
+ drivers/net/ethernet/intel/igb/igb_main.c | 6 ++++++
+ 1 file changed, 6 insertions(+)
+
+--- a/drivers/net/ethernet/intel/igb/igb_main.c
++++ b/drivers/net/ethernet/intel/igb/igb_main.c
+@@ -1020,6 +1020,12 @@ static void igb_reset_q_vector(struct ig
+ 	if (!q_vector)
+ 		return;
+ 
++	/* Coming from igb_set_interrupt_capability, the vectors are not yet
++	 * allocated. So, q_vector is NULL so we should stop here.
++	 */
++	if (!q_vector)
++		return;
++
+ 	if (q_vector->tx.ring)
+ 		adapter->tx_ring[q_vector->tx.ring->queue_index] = NULL;
+