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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Tue, 14 Jul 2020 15:27:38 +0200
Message-ID: <CAJZ5v0gDwtZ+oYSrj_Ta56QPSeW3OSq4XHkiubOHr4xki7muPw@mail.gmail.com>
Subject: Re: [PATCH 8/14 v3] PCI/ACPI: Check the return value of pcie_capability_read_*()
To:     "Saheed O. Bolarinwa" <refactormyself@gmail.com>
Cc:     Shuah Khan <skhan@linuxfoundation.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        Linux PCI <linux-pci@vger.kernel.org>,
        linux-kernel-mentees@lists.linuxfoundation.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Mon, Jul 13, 2020 at 6:55 PM Saheed O. Bolarinwa
<refactormyself@gmail.com> wrote:
>
> From: Bolarinwa Olayemi Saheed <refactormyself@gmail.com>
>
> On failure pcie_capability_read_dword() sets it's last parameter,
> val to 0.
> However, with Patch 14/14, it is possible that val is set to ~0 on
> failure. This would introduce a bug because (x & x) == (~0 & x).
>
> This bug can be avoided if the return value of pcie_capability_read_word
> is checked to confirm success.
>
> Check the return value of pcie_capability_read_word() to ensure success.
>
> Suggested-by: Bjorn Helgaas <bjorn@helgaas.com>
> Signed-off-by: Bolarinwa Olayemi Saheed <refactormyself@gmail.com>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
>  drivers/pci/pci-acpi.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> index 7224b1e5f2a8..39eb816bc3b8 100644
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -248,12 +248,13 @@ static bool pcie_root_rcb_set(struct pci_dev *dev)
>  {
>         struct pci_dev *rp = pcie_find_root_port(dev);
>         u16 lnkctl;
> +       int ret;
>
>         if (!rp)
>                 return false;
>
> -       pcie_capability_read_word(rp, PCI_EXP_LNKCTL, &lnkctl);
> -       if (lnkctl & PCI_EXP_LNKCTL_RCB)
> +       ret = pcie_capability_read_word(rp, PCI_EXP_LNKCTL, &lnkctl);
> +       if (!ret && (lnkctl & PCI_EXP_LNKCTL_RCB))
>                 return true;
>
>         return false;
> @@ -792,12 +793,13 @@ bool pciehp_is_native(struct pci_dev *bridge)
>  {
>         const struct pci_host_bridge *host;
>         u32 slot_cap;
> +       int ret;
>
>         if (!IS_ENABLED(CONFIG_HOTPLUG_PCI_PCIE))
>                 return false;
>
> -       pcie_capability_read_dword(bridge, PCI_EXP_SLTCAP, &slot_cap);
> -       if (!(slot_cap & PCI_EXP_SLTCAP_HPC))
> +       ret = pcie_capability_read_dword(bridge, PCI_EXP_SLTCAP, &slot_cap);
> +       if (ret || !(slot_cap & PCI_EXP_SLTCAP_HPC))
>                 return false;
>
>         if (pcie_ports_native)
> --
> 2.18.2
>