[PATCH 3.14 119/228] igb: Fix Null-pointer dereference in igb_reset_q_vector

[Greg Kroah-Hartman]

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christoph Paasch <christoph.paasch@xxxxxxxxxxxx>

commit cb06d102327eadcd1bdc480bfd9f8876251d1007 upstream.

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@xxxxxxxxx>
Signed-off-by: Christoph Paasch <christoph.paasch@xxxxxxxxxxxx>
Tested-by: Jeff Pieper <jeffrey.e.pieper@xxxxxxxxx>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 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
@@ -1014,6 +1014,12 @@ static void igb_reset_q_vector(struct ig
 {
 	struct igb_q_vector *q_vector = adapter->q_vector[v_idx];
 
+	/* 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;
 


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