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

[Frederic Barrat <fbarrat@linux.ibm.com>]

On 21/11/2022 16:43, 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>
> ---


Thanks for fixing it!

Acked-by: Frederic Barrat <fbarrat@linux.ibm.com>

   Fred


> 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;
>   }
>