Re: [bug report] PCI/ACPI: Fix allocated memory release on error in pci_acpi_scan_root()

[Dan Carpenter <dan.carpenter@linaro.org>]

On Thu, Jun 12, 2025 at 01:12:43PM +0800, Zhe Qiao wrote:
> Hi Dan Carpenter,
> 
> On Wed, Jun 11, 2025 at 11:15 PM Dan Carpenter <dan.carpenter@linaro.org> wrote:
> >
> > Hello Zhe Qiao,
> >
> > Commit 631b2af2f357 ("PCI/ACPI: Fix allocated memory release on error
> > in pci_acpi_scan_root()") from Apr 30, 2025 (linux-next), leads to
> > the following Smatch static checker warning:
> >
> >         drivers/pci/pci-acpi.c:1712 pci_acpi_scan_root()
> >         error: double free of 'root_ops' (line 1711)
> >
> > drivers/pci/pci-acpi.c
> >     1667 struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
> >     1668 {
> >     1669         struct acpi_pci_generic_root_info *ri;
> >     1670         struct pci_bus *bus, *child;
> >     1671         struct acpi_pci_root_ops *root_ops;
> >     1672         struct pci_host_bridge *host;
> >     1673
> >     1674         ri = kzalloc(sizeof(*ri), GFP_KERNEL);
> >     1675         if (!ri)
> >     1676                 return NULL;
> >     1677
> >     1678         root_ops = kzalloc(sizeof(*root_ops), GFP_KERNEL);
> >     1679         if (!root_ops)
> >     1680                 goto free_ri;
> >     1681
> >     1682         ri->cfg = pci_acpi_setup_ecam_mapping(root);
> >     1683         if (!ri->cfg)
> >     1684                 goto free_root_ops;
> >     1685
> >     1686         root_ops->release_info = pci_acpi_generic_release_info;
> >     1687         root_ops->prepare_resources = pci_acpi_root_prepare_resources;
> >     1688         root_ops->pci_ops = (struct pci_ops *)&ri->cfg->ops->pci_ops;
> >     1689         bus = acpi_pci_root_create(root, root_ops, &ri->common, ri->cfg);
> >     1690         if (!bus)
> >     1691                 goto free_cfg;
> >
> > The acpi_pci_root_create() function frees root_ops on error in
> > pci_acpi_generic_release_info().  I think there is only one error
> > path where it frees "ri->cfg".  I probably would advise you to re-write
> > the the error handling in acpi_pci_root_create().
> 
> Thanks, this is really an unexpected gain for me. I didn't notice that
> the memory
> release operation has been implemented in the pci_acpi_generic_release_info
> function. But I think it's a bit unclear in the code logic to release
> these memories
> in the pci_acpi_generic_release_info function. As you pointed out, I
> want to let the
> pci_acpi_generic_release_info function return directly, and put all the memory
> release operations into the error handling part of the
> pci_acpi_scan_root function.
> What do you think of this? If you have any better suggestions, please
> let me know.
> 

Either way is fine with me.  I understand why we tried to do the
free in acpi_pci_root_create() but that approached didn't free
"sysdata" reliably so it's not like we can just revert your commit.

If you take your approach you'll have to change pci_acpi_scan_root() as
well.

regards,
dan carpenter