e1000e: write protect ICHx NVM to prevent malicious write/erase

Set the hardware to ignore all write/erase cycles to the GbE region in
the ICHx NVM.  This feature can be disabled by the WriteProtectNVM module
parameter (enabled by default) only after a hardware reset, but
the machine must be power cycled before trying to enable writes.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
CC: arjan@linux.intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/net/e1000e/ethtool.c b/drivers/net/e1000e/ethtool.c
index e21c9e0..5ed8e13 100644
--- a/drivers/net/e1000e/ethtool.c
+++ b/drivers/net/e1000e/ethtool.c
@@ -529,6 +529,9 @@
 	if (eeprom->magic != (adapter->pdev->vendor | (adapter->pdev->device << 16)))
 		return -EFAULT;
 
+	if (adapter->flags & FLAG_READ_ONLY_NVM)
+		return -EINVAL;
+
 	max_len = hw->nvm.word_size * 2;
 
 	first_word = eeprom->offset >> 1;