linux-kernel - Re: [PATCH 2/2] virtio-net: Prevent NULL dereference

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Message-ID: <20110926184703.GB22278@redhat.com>
Date:	Mon, 26 Sep 2011 21:47:03 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
	kvm@...r.kernel.org
Subject: Re: [PATCH 2/2] virtio-net: Prevent NULL dereference

On Mon, Sep 26, 2011 at 08:41:09PM +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@...tcorp.com.au>
> Cc: "Michael S. Tsirkin" <mst@...hat.com>
> Cc: virtualization@...ts.linux-foundation.org
> Cc: netdev@...r.kernel.org
> Cc: kvm@...r.kernel.org
> Signed-off-by: Sasha Levin <levinsasha928@...il.com>

Hmm, another protection against a buggy device, right?
No problem with that, but let's discard the packet
and print a disgnostic, so that the user can discover
what happened.

> ---
>  drivers/net/virtio_net.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 64e0717..8d32c1e 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -198,7 +198,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
>  	len -= copy;
>  	offset += copy;
>  
> -	while (len) {
> +	while (len && page) {
>  		set_skb_frag(skb, page, offset, &len);
>  		page = (struct page *)page->private;
>  		offset = 0;
> -- 
> 1.7.6.1
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