linux-kernel - Re: [PATCH] PCI/ACPI: Fix double free bug in pci_acpi_scan

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Message-ID: <CAJZ5v0jpJLMZYONVxg3ncEDEKoTy0tyaoBfCSnRrhJYmF8fngA@mail.gmail.com>
Date: Mon, 16 Jun 2025 13:15:01 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Zhe Qiao <qiaozhe@...as.ac.cn>
Cc: sashal@...nel.org, rafael@...nel.org, lenb@...nel.org, bhelgaas@...gle.com, 
	kwilczynski@...nel.org, linux-kernel@...r.kernel.org, 
	linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH] PCI/ACPI: Fix double free bug in pci_acpi_scan_root() function

On Mon, Jun 16, 2025 at 10:44 AM Zhe Qiao <qiaozhe@...as.ac.cn> wrote:
>
> Fix the double free bug introduced in the patch "PCI/ACPI: Fix
> allocated memory release on error in pci_acpi_scan_root()".

More details, please.

What's the bug and why is this the best fix?

> Fixes: 631b2af2f357 ("PCI/ACPI: Fix allocated memory release on error in pci_acpi_scan_root()")
> Signed-off-by: Zhe Qiao <qiaozhe@...as.ac.cn>
> ---
>  drivers/pci/pci-acpi.c | 10 +---------
>  1 file changed, 1 insertion(+), 9 deletions(-)
>
> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> index b78e0e417324..49b72596ae37 100644
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -1653,15 +1653,7 @@ pci_acpi_setup_ecam_mapping(struct acpi_pci_root *root)
>  }
>
>  /* release_info: free resources allocated by init_info */
> -static void pci_acpi_generic_release_info(struct acpi_pci_root_info *ci)
> -{
> -       struct acpi_pci_generic_root_info *ri;
> -
> -       ri = container_of(ci, struct acpi_pci_generic_root_info, common);
> -       pci_ecam_free(ri->cfg);
> -       kfree(ci->ops);
> -       kfree(ri);
> -}
> +static void pci_acpi_generic_release_info(struct acpi_pci_root_info *ci) {}

Why don't you add a check for info->ops->release_info to
__acpi_pci_root_release_info() and drop this altogether?

>  /* Interface called from ACPI code to setup PCI host controller */
>  struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
> --