From 0845d45e900cad5f7f855a7a6a21c33477800b1f Mon Sep 17 00:00:00 2001
From: Jia-Ju Bai <baijiaju1990@163.com>
Date: Wed, 5 Aug 2015 18:16:10 +0800
Subject: [PATCH] e1000e: Modify Tx/Rx configurations to avoid null pointer
 dereferences in e1000_open

When e1000e_setup_rx_resources is failed in e1000_open,
e1000e_free_tx_resources in "err_setup_rx" segment is executed.
"writel(0, tx_ring->head)" statement in e1000_clean_tx_ring
in e1000e_free_tx_resources will cause a null poonter dereference(crash),
because "tx_ring->head" is only assigned in e1000_configure_tx
in e1000_configure, but it is after e1000e_setup_rx_resources.

This patch moves head/tail register writing to e1000_configure_tx/rx,
which can fix this problem. It is inspired by igb_configure_tx_ring
in the igb driver.

Specially, thank Alexander Duyck for his valuable suggestion.

Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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