Re: [PATCH v8 0/7] Add pci_dev_for_each_resource() helper and update users

On Fri, May 12, 2023 at 01:56:29PM +0300, Andy Shevchenko wrote:
> On Tue, May 09, 2023 at 01:21:22PM -0500, Bjorn Helgaas wrote:
> > On Tue, Apr 04, 2023 at 11:11:01AM -0500, Bjorn Helgaas wrote:
> > > On Thu, Mar 30, 2023 at 07:24:27PM +0300, Andy Shevchenko wrote:
> > > > Provide two new helper macros to iterate over PCI device resources and
> > > > convert users.
> > 
> > > Applied 2-7 to pci/resource for v6.4, thanks, I really like this!
> > 
> > This is 09cc90063240 ("PCI: Introduce pci_dev_for_each_resource()")
> > upstream now.
> > 
> > Coverity complains about each use,
> 
> It needs more clarification here. Use of reduced variant of the
> macro or all of them? If the former one, then I can speculate that
> Coverity (famous for false positives) simply doesn't understand `for
> (type var; var ...)` code.

True, Coverity finds false positives.  It flagged every use in
drivers/pci and drivers/pnp.  It didn't mention the arch/alpha, arm,
mips, powerpc, sh, or sparc uses, but I think it just didn't look at
those.

It flagged both:

  pbus_size_io    pci_dev_for_each_resource(dev, r)
  pbus_size_mem   pci_dev_for_each_resource(dev, r, i)

Here's a spreadsheet with a few more details (unfortunately I don't
know how to make it dump the actual line numbers or analysis like I
pasted below, so "pci_dev_for_each_resource" doesn't appear).  These
are mostly in the "Drivers-PCI" component.

https://docs.google.com/spreadsheets/d/1ohOJwxqXXoDUA0gwopgk-z-6ArLvhN7AZn4mIlDkHhQ/edit?usp=sharing

These particular reports are in the "High Impact Outstanding" tab.

> >	sample below from
> > drivers/pci/vgaarb.c.  I didn't investigate at all, so it might be a
> > false positive; just FYI.
> > 
> > 	  1. Condition screen_info.capabilities & (2U /* 1 << 1 */), taking true branch.
> >   556        if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
> >   557                base |= (u64)screen_info.ext_lfb_base << 32;
> >   558
> >   559        limit = base + size;
> >   560
> >   561        /* Does firmware framebuffer belong to us? */
> > 	  2. Condition __b < PCI_NUM_RESOURCES, taking true branch.
> > 	  3. Condition (r = &pdev->resource[__b]) , (__b < PCI_NUM_RESOURCES), taking true branch.
> > 	  6. Condition __b < PCI_NUM_RESOURCES, taking true branch.
> > 	  7. cond_at_most: Checking __b < PCI_NUM_RESOURCES implies that __b may be up to 16 on the true branch.
> > 	  8. Condition (r = &pdev->resource[__b]) , (__b < PCI_NUM_RESOURCES), taking true branch.
> > 	  11. incr: Incrementing __b. The value of __b may now be up to 17.
> > 	  12. alias: Assigning: r = &pdev->resource[__b]. r may now point to as high as element 17 of pdev->resource (which consists of 17 64-byte elements).
> > 	  13. Condition __b < PCI_NUM_RESOURCES, taking true branch.
> > 	  14. Condition (r = &pdev->resource[__b]) , (__b < PCI_NUM_RESOURCES), taking true branch.
> >   562        pci_dev_for_each_resource(pdev, r) {
> > 	  4. Condition resource_type(r) != 512, taking true branch.
> > 	  9. Condition resource_type(r) != 512, taking true branch.
> > 
> >   CID 1529911 (#1 of 1): Out-of-bounds read (OVERRUN)
> >   15. overrun-local: Overrunning array of 1088 bytes at byte offset 1088 by dereferencing pointer r. [show details]
> >   563                if (resource_type(r) != IORESOURCE_MEM)
> > 	  5. Continuing loop.
> > 	  10. Continuing loop.
> >   564                        continue;
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
>