Re: [PATCH v2] ocxl: fix pci device refcount leak when calling get_function_0()

[Andrew Donnellan <ajd@linux.ibm.com>]

On Mon, 2022-11-21 at 23:43 +0800, Yang Yingliang wrote:
> get_function_0() calls pci_get_domain_bus_and_slot(), as comment
> says, it returns a pci device with refcount increment, so after
> using it, pci_dev_put() needs be called.
> 
> Get the device reference when get_function_0() is not called, so
> pci_dev_put() can be called in the error path and callers
> unconditionally. And add comment above get_dvsec_vendor0() to tell
> callers to call pci_dev_put().
> 
> Fixes: 87db7579ebd5 ("ocxl: control via sysfs whether the FPGA is
> reloaded on a link reset")
> Suggested-by: Andrew Donnellan <ajd@linux.ibm.com>
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>

Looks good!

Acked-by: Andrew Donnellan <ajd@linux.ibm.com>

> ---
> v1 -> v2:
>   Add comment above get_dvsec_vendor0().
>   Get reference where dev is function 0, and call pci_dev_put()
>   unconditionally in callers.
> ---
>  drivers/misc/ocxl/config.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/misc/ocxl/config.c b/drivers/misc/ocxl/config.c
> index e401a51596b9..92ab49705f64 100644
> --- a/drivers/misc/ocxl/config.c
> +++ b/drivers/misc/ocxl/config.c
> @@ -193,6 +193,18 @@ static int read_dvsec_vendor(struct pci_dev
> *dev)
>         return 0;
>  }
>  
> +/**
> + * get_dvsec_vendor0() - Find a related PCI device (function 0)
> + * @dev: PCI device to match
> + * @dev0: The PCI device (function 0) found
> + * @out_pos: The position of PCI device (function 0)
> + *
> + * Returns 0 on success, negative on failure.
> + *
> + * NOTE: If it's successful, the reference of dev0 is increased,
> + * so after using it, the callers must call pci_dev_put() to give
> + * up the reference.
> + */
>  static int get_dvsec_vendor0(struct pci_dev *dev, struct pci_dev
> **dev0,
>                              int *out_pos)
>  {
> @@ -202,10 +214,14 @@ static int get_dvsec_vendor0(struct pci_dev
> *dev, struct pci_dev **dev0,
>                 dev = get_function_0(dev);
>                 if (!dev)
>                         return -1;
> +       } else {
> +               dev = pci_dev_get(dev);
>         }
>         pos = find_dvsec(dev, OCXL_DVSEC_VENDOR_ID);
> -       if (!pos)
> +       if (!pos) {
> +               pci_dev_put(dev);
>                 return -1;
> +       }
>         *dev0 = dev;
>         *out_pos = pos;
>         return 0;
> @@ -222,6 +238,7 @@ int ocxl_config_get_reset_reload(struct pci_dev
> *dev, int *val)
>  
>         pci_read_config_dword(dev0, pos +
> OCXL_DVSEC_VENDOR_RESET_RELOAD,
>                               &reset_reload);
> +       pci_dev_put(dev0);
>         *val = !!(reset_reload & BIT(0));
>         return 0;
>  }
> @@ -243,6 +260,7 @@ int ocxl_config_set_reset_reload(struct pci_dev
> *dev, int val)
>                 reset_reload &= ~BIT(0);
>         pci_write_config_dword(dev0, pos +
> OCXL_DVSEC_VENDOR_RESET_RELOAD,
>                                reset_reload);
> +       pci_dev_put(dev0);
>         return 0;
>  }
>  

-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@linux.ibm.com   IBM Australia Limited