Re: [PATCH] PCI: hisi: fix the hisi_pcie_cfg_read bug when size=4

[Bjorn Helgaas <helgaas@kernel.org>]

On Fri, Dec 04, 2015 at 04:43:34PM -0600, Bjorn Helgaas wrote:
> On Fri, Nov 27, 2015 at 12:58:00PM +0800, Dongdong Liu wrote:
> > Current hisi_pcie_cfg_read code read the RC configuration space,
> > this has a problem that the output parameter "*val" have not been
> > assigned when size=4, so we fix the bug by "*val = reg_val" when size=4.
> > 
> > Signed-off-by: Dongdong Liu <liudongdong3@huawei.com>
> 
> Wow, that's a pretty egregious bug.  Was the hisi driver ever tested
> at all?  We use dword reads in pci_bus_read_dev_vendor_id() to
> enumerate devices, so if those didn't return valid data, nothing at
> all should have worked.
> 
> I tentatively put this on my for-linus branch for v4.4, but I wonder
> whether it might be smarter to revert the driver completely until I
> have more confidence in it.
> 
> What sort of testing have you done on this driver?

Since I haven't heard anything about whether this driver was ever
tested, I dropped this patch from my for-linus branch and I reverted
the entire hisi driver.

Let me know when you have some testing results, and I'll take another
look at it.

Bjorn

> > ---
> >  drivers/pci/host/pcie-hisi.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/host/pcie-hisi.c b/drivers/pci/host/pcie-hisi.c
> > index 35457ec..da677b1 100644
> > --- a/drivers/pci/host/pcie-hisi.c
> > +++ b/drivers/pci/host/pcie-hisi.c
> > @@ -61,7 +61,9 @@ static int hisi_pcie_cfg_read(struct pcie_port *pp, int where, int size,
> >  		*val = *(u8 __force *) walker;
> >  	else if (size == 2)
> >  		*val = *(u16 __force *) walker;
> > -	else if (size != 4)
> > +	else if (size == 4)
> > +		*val = reg_val;
> > +	else
> >  		return PCIBIOS_BAD_REGISTER_NUMBER;
> >  
> >  	return PCIBIOS_SUCCESSFUL;
> > -- 
> > 1.9.1
> > 
> > --
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