Patch "igb: re-assign hw address pointer on reset after PCI error" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

igb: re-assign hw address pointer on reset after PCI error

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
igb-re-assign-hw-address-pointer-on-reset-after-pci-error.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Guilherme G Piccoli <[email protected]>
Date: Thu, 10 Nov 2016 16:46:43 -0200
Subject: igb: re-assign hw address pointer on reset after PCI error

From: Guilherme G Piccoli <[email protected]>

[ Upstream commit 69b97cf6dbce7403845a28bbc75d57f5be7b12ac ]

Whenever the igb driver detects the result of a read operation returns a value composed only by F's (like 0xFFFFFFFF), it will detach the net_device, clear the hw_addr pointer and warn to the user that adapter's link is lost - those steps happen on igb_rd32().

In case a PCI error happens on Power architecture, there's a recovery mechanism called EEH, that will reset the PCI slot and call driver's handlers to reset the adapter and network functionality as well.

We observed that once hw_addr is NULL after the error is detected on igb_rd32(), it's never assigned back, so in the process of resetting the network functionality we got a NULL pointer dereference in both igb_configure_tx_ring() and igb_configure_rx_ring(). In order to avoid such bug, this patch re-assigns the hw_addr value in the slot_reset handler.

---
 drivers/net/ethernet/intel/igb/igb_main.c |    5 +++++
 1 file changed, 5 insertions(+)

@@ -7658,6 +7658,11 @@ static pci_ers_result_t igb_io_slot_rese
 		pci_enable_wake(pdev, PCI_D3hot, 0);
 		pci_enable_wake(pdev, PCI_D3cold, 0);
 
+		/* In case of PCI error, adapter lose its HW address
+		 * so we should re-assign it here.
+		 */
+		hw->hw_addr = adapter->io_addr;
+
 		igb_reset(adapter);
 		wr32(E1000_WUS, ~0);
 		result = PCI_ERS_RESULT_RECOVERED;

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/igb-re-assign-hw-address-pointer-on-reset-after-pci-error.patch