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

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

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.

>       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