Subject: Re: [PATCH net v2] igb: re-assign hw address pointer on reset after PCI error

From: "Keller, Jacob E" <[email-masked]>
Date: Fri, 2 Dec 2016 16:41:59 +0000

On Fri, 2016-12-02 at 10:55 -0200, Guilherme G. Piccoli wrote:
> On 11/10/2016 04:46 PM, Guilherme G. Piccoli wrote:
> > 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.
> > 
> > Reported-by: Anthony H. Thai <[email-masked]>
> > Reported-by: Harsha Thyagaraja <[email-masked]>
> > Signed-off-by: Guilherme G. Piccoli <[email-masked]>
> > ---
> >  drivers/net/ethernet/intel/igb/igb_main.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/net/ethernet/intel/igb/igb_main.c
> > b/drivers/net/ethernet/intel/igb/igb_main.c
> > index edc9a6a..136ee9e 100644
> > --- a/drivers/net/ethernet/intel/igb/igb_main.c
> > +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> > @@ -7878,6 +7878,11 @@ static pci_ers_result_t
> > igb_io_slot_reset(struct pci_dev *pdev)
> >  		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;
> > 
> 
> Ping?
> 
> Sorry to annoy, any news on this?
> Thanks in advance!
> 
> Cheers,
> 
> 
> Guilherme
> 

This seems reasonable. It's similar to what fm10k driver does under
this circumstance.

Thanks,
Jake