Re: [PATCH] PCI/proc: check __get_user() return value in proc_bus_pci_write()

["Krzysztof Wilczyński" <kw@linux.com>]

Hello,

> Check __get_user() and return -EFAULT on failure.
[...]
> @@ -136,7 +136,10 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf,
>  
>  	if ((pos & 1) && cnt) {
>  		unsigned char val;
> -		__get_user(val, buf);
> +		if (__get_user(val, buf)) {
> +			ret = -EFAULT;
> +			goto out;
> +		}

We could move to get_user() here.  This would allow you to drop
the access_ok(), too, as get_user() would return -EFAULT on error.

So, something simple, like:

  if (get_user(val, buf))
  	goto err;

> +out:

Use "err" for a single goto label for the error path.

>  	pci_config_pm_runtime_put(dev);
> -
>  	*ppos = pos;
> -	i_size_write(ino, dev->cfg_size);
> -	return nbytes;
> +	if (ret > 0)
> +		i_size_write(ino, dev->cfg_size);
> +	return ret;

This can be kept simple:

  err:
  	pci_config_pm_runtime_put(dev);
  	return -EFAULT;

The i_size_write() is such an unfortunate band-aid, but unless we have a
way to set the size before the procfs entry is created/made visible, then
the problem that this aims to fix is here to stay for now, see:

  ecb3908046ce ("pci: write file size to inode on proc bus file write")

Having said all that, since you are looking at proc_bus_pci_write(),
then perhaps an update to proc_bus_pci_read() to use put_user() would
also be prudent.

Thank you!

	Krzysztof