linux-kernel - Re: [PATCH v8 03/50] mic_virtio: robust feature array size calculation

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Date:	Tue, 2 Dec 2014 11:13:46 +0100
From:	Thomas Huth <thuth@...ux.vnet.ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	linux-kernel@...r.kernel.org, David Miller <davem@...emloft.net>,
	cornelia.huck@...ibm.com, rusty@....ibm.com, nab@...ux-iscsi.org,
	pbonzini@...hat.com, dahi@...ux.vnet.ibm.com,
	Rusty Russell <rusty@...tcorp.com.au>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Siva Yerramreddy <yshivakrishna@...il.com>
Subject: Re: [PATCH v8 03/50] mic_virtio: robust feature array size
 calculation

On Mon, 1 Dec 2014 18:02:59 +0200
"Michael S. Tsirkin" <mst@...hat.com> wrote:

> mic reads sizeof(vdev->features) bits from device, but in fact it stores
> bits in local features variable. use sizeof(features) to make code
> robust against future changes extending sizeof(vdev->features).
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
>  drivers/misc/mic/card/mic_virtio.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/misc/mic/card/mic_virtio.c b/drivers/misc/mic/card/mic_virtio.c
> index 4f070ad..d5da9ff 100644
> --- a/drivers/misc/mic/card/mic_virtio.c
> +++ b/drivers/misc/mic/card/mic_virtio.c
> @@ -76,8 +76,7 @@ static u32 mic_get_features(struct virtio_device *vdev)
>  	u8 __iomem *in_features = mic_vq_features(desc);
>  	int feature_len = ioread8(&desc->feature_len);
> 
> -	bits = min_t(unsigned, feature_len,
> -		sizeof(vdev->features)) * 8;
> +	bits = min_t(unsigned, feature_len, sizeof(features)) * 8;
>  	for (i = 0; i < bits; i++)
>  		if (ioread8(&in_features[i / 8]) & (BIT(i % 8)))
>  			features |= BIT(i);

Reviewed-by: Thomas Huth <thuth@...ux.vnet.ibm.com>

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