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SubjectRe: [PATCH v2 2/2] virtio-net: Prevent NULL dereference
On Wed, Sep 28, 2011 at 05:40:55PM +0300, Sasha Levin wrote:
> This patch prevents a NULL dereference when the user has passed a length
> longer than an actual buffer to virtio-net.
>
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: virtualization@lists.linux-foundation.org
> Cc: netdev@vger.kernel.org
> Cc: kvm@vger.kernel.org
> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
> ---
> drivers/net/virtio_net.c | 12 +++++++++++-
> 1 files changed, 11 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index bde0dec..4a53d2a 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -208,12 +208,22 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> return NULL;
> }
>
> - while (len) {
> + while (len && page) {
> set_skb_frag(skb, page, offset, &len);
> page = (struct page *)page->private;
> offset = 0;
> }
>
> + /*
> + * This is the case where we ran out of pages in our linked list, but
> + * supposedly have more data to read.

Again, let's clarify that this only happens with broken devices.

> + */
> + if (len > 0) {
> + pr_debug("%s: missing data to assemble skb\n", skb->dev->name);
> + dev_kfree_skb(skb);
> + return NULL;
> + }
> +
> if (page)
> give_pages(vi, page);
>
> --
> 1.7.6.1


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