netdev - Re: [PATCH 2/3] vhost-net: fix to check the return value of copy_to/from

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Date:	Thu, 27 May 2010 13:48:45 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
Cc:	kvm@...r.kernel.org, virtualization@...ts.osdl.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH 2/3] vhost-net: fix to check the return value of
	copy_to/from_user() correctly

On Thu, May 27, 2010 at 07:01:58PM +0900, Takuya Yoshikawa wrote:
> copy_to/from_user() returns the number of bytes that could not be copied.
> 
> So we need to check if it is not zero, and in that case, we should return
> the error number -EFAULT rather than directly return the return value from
> copy_to/from_user().
> 
> Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>

Thanks, applied.

> ---
>  drivers/vhost/net.c |   14 +++++++-------
>  1 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index aa88911..0f41c91 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -593,17 +593,17 @@ static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
>  	int r;
>  	switch (ioctl) {
>  	case VHOST_NET_SET_BACKEND:
> -		r = copy_from_user(&backend, argp, sizeof backend);
> -		if (r < 0)
> -			return r;
> +		if (copy_from_user(&backend, argp, sizeof backend))
> +			return -EFAULT;
>  		return vhost_net_set_backend(n, backend.index, backend.fd);
>  	case VHOST_GET_FEATURES:
>  		features = VHOST_FEATURES;
> -		return copy_to_user(featurep, &features, sizeof features);
> +		if (copy_to_user(featurep, &features, sizeof features))
> +			return -EFAULT;
> +		return 0;
>  	case VHOST_SET_FEATURES:
> -		r = copy_from_user(&features, featurep, sizeof features);
> -		if (r < 0)
> -			return r;
> +		if (copy_from_user(&features, featurep, sizeof features))
> +			return -EFAULT;
>  		if (features & ~VHOST_FEATURES)
>  			return -EOPNOTSUPP;
>  		return vhost_net_set_features(n, features);
> -- 
> 1.7.0.4
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