Patchwork [v2,1/2] virtio-net: Verify page list size before fitting into skb

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Submitter Sasha Levin
Date Sept. 28, 2011, 2:40 p.m.
Message ID <1317220855-9352-1-git-send-email-levinsasha928@gmail.com>
Download mbox | patch
Permalink /patch/116799/
State Accepted
Delegated to: David Miller
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Comments

Sasha Levin - Sept. 28, 2011, 2:40 p.m.
This patch verifies that the length of a buffer stored in a linked list
of pages is small enough to fit into a skb.

If the size is larger than a max size of a skb, it means that we shouldn't
go ahead building skbs anyway since we won't be able to send the buffer as
the user requested.

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 |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)
David Miller - Oct. 3, 2011, 6:19 p.m.
From: Sasha Levin <levinsasha928@gmail.com>
Date: Wed, 28 Sep 2011 17:40:54 +0300

> This patch verifies that the length of a buffer stored in a linked list
> of pages is small enough to fit into a skb.
> 
> If the size is larger than a max size of a skb, it means that we shouldn't
> go ahead building skbs anyway since we won't be able to send the buffer as
> the user requested.
> 
> 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>

Michael, tell me what's happening with these two virtio-net bug fixes.

Thanks.
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Michael S. Tsirkin - Oct. 3, 2011, 6:42 p.m.
On Mon, Oct 03, 2011 at 02:19:51PM -0400, David Miller wrote:
> From: Sasha Levin <levinsasha928@gmail.com>
> Date: Wed, 28 Sep 2011 17:40:54 +0300
> 
> > This patch verifies that the length of a buffer stored in a linked list
> > of pages is small enough to fit into a skb.
> > 
> > If the size is larger than a max size of a skb, it means that we shouldn't
> > go ahead building skbs anyway since we won't be able to send the buffer as
> > the user requested.
> > 
> > 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>
> 
> Michael, tell me what's happening with these two virtio-net bug fixes.
> 
> Thanks.

Thanks for the reminder.
They are more enhancements than bugfixes, in that both help debug buggy
hypervisors. So net-next material.
Patch 1 is ok patch 2 would benefit from a slightly clearer comment.
Michael S. Tsirkin - Oct. 3, 2011, 7:04 p.m.
On Wed, Sep 28, 2011 at 05:40:54PM +0300, Sasha Levin wrote:
> This patch verifies that the length of a buffer stored in a linked list
> of pages is small enough to fit into a skb.
> 
> If the size is larger than a max size of a skb, it means that we shouldn't
> go ahead building skbs anyway since we won't be able to send the buffer as
> the user requested.
> 
> 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 |   13 +++++++++++++
>  1 files changed, 13 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 0c7321c..bde0dec 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -195,6 +195,19 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
>  	len -= copy;
>  	offset += copy;
>  
> +	/*
> +	 * Verify that we can indeed put this data into a skb.
> +	 * This is here to handle cases when the device erroneously
> +	 * tries to receive more than is possible. This is usually
> +	 * the case of a broken device.
> +	 */
> +	if (unlikely(len > MAX_SKB_FRAGS * PAGE_SIZE)) {
> +		if (net_ratelimit())
> +			pr_debug("%s: too much data\n", skb->dev->name);
> +		dev_kfree_skb(skb);
> +		return NULL;
> +	}
> +

BTW, receive_mergeable does
                        pr_debug("%s: packet too long\n", skb->dev->name);
                        skb->dev->stats.rx_length_errors++;

which makes sense.

>  	while (len) {
>  		set_skb_frag(skb, page, offset, &len);
>  		page = (struct page *)page->private;
> -- 
> 1.7.6.1
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Sasha Levin - Oct. 5, 2011, 1:50 p.m.
On Mon, 2011-10-03 at 21:04 +0200, Michael S. Tsirkin wrote:
> On Wed, Sep 28, 2011 at 05:40:54PM +0300, Sasha Levin wrote:
> > This patch verifies that the length of a buffer stored in a linked list
> > of pages is small enough to fit into a skb.
> > 
> > If the size is larger than a max size of a skb, it means that we shouldn't
> > go ahead building skbs anyway since we won't be able to send the buffer as
> > the user requested.
> > 
> > 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 |   13 +++++++++++++
> >  1 files changed, 13 insertions(+), 0 deletions(-)
> > 
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 0c7321c..bde0dec 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -195,6 +195,19 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> >  	len -= copy;
> >  	offset += copy;
> >  
> > +	/*
> > +	 * Verify that we can indeed put this data into a skb.
> > +	 * This is here to handle cases when the device erroneously
> > +	 * tries to receive more than is possible. This is usually
> > +	 * the case of a broken device.
> > +	 */
> > +	if (unlikely(len > MAX_SKB_FRAGS * PAGE_SIZE)) {
> > +		if (net_ratelimit())
> > +			pr_debug("%s: too much data\n", skb->dev->name);
> > +		dev_kfree_skb(skb);
> > +		return NULL;
> > +	}
> > +
> 
> BTW, receive_mergeable does
>                         pr_debug("%s: packet too long\n", skb->dev->name);
>                         skb->dev->stats.rx_length_errors++;
> 
> which makes sense.

Do you think we should increase rx_length_errors here as well?
Michael S. Tsirkin - Oct. 5, 2011, 6:59 p.m.
On Wed, Oct 05, 2011 at 03:50:54PM +0200, Sasha Levin wrote:
> On Mon, 2011-10-03 at 21:04 +0200, Michael S. Tsirkin wrote:
> > On Wed, Sep 28, 2011 at 05:40:54PM +0300, Sasha Levin wrote:
> > > This patch verifies that the length of a buffer stored in a linked list
> > > of pages is small enough to fit into a skb.
> > > 
> > > If the size is larger than a max size of a skb, it means that we shouldn't
> > > go ahead building skbs anyway since we won't be able to send the buffer as
> > > the user requested.
> > > 
> > > 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 |   13 +++++++++++++
> > >  1 files changed, 13 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index 0c7321c..bde0dec 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -195,6 +195,19 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> > >  	len -= copy;
> > >  	offset += copy;
> > >  
> > > +	/*
> > > +	 * Verify that we can indeed put this data into a skb.
> > > +	 * This is here to handle cases when the device erroneously
> > > +	 * tries to receive more than is possible. This is usually
> > > +	 * the case of a broken device.
> > > +	 */
> > > +	if (unlikely(len > MAX_SKB_FRAGS * PAGE_SIZE)) {
> > > +		if (net_ratelimit())
> > > +			pr_debug("%s: too much data\n", skb->dev->name);
> > > +		dev_kfree_skb(skb);
> > > +		return NULL;
> > > +	}
> > > +
> > 
> > BTW, receive_mergeable does
> >                         pr_debug("%s: packet too long\n", skb->dev->name);
> >                         skb->dev->stats.rx_length_errors++;
> > 
> > which makes sense.
> 
> Do you think we should increase rx_length_errors here as well?

this is all debugging tool for devices/drivers, right?
so maybe not worth the noise.

> -- 
> 
> Sasha.
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David Miller - Oct. 6, 2011, 7:41 p.m.
From: Sasha Levin <levinsasha928@gmail.com>
Date: Wed, 28 Sep 2011 17:40:54 +0300

> This patch verifies that the length of a buffer stored in a linked list
> of pages is small enough to fit into a skb.
> 
> If the size is larger than a max size of a skb, it means that we shouldn't
> go ahead building skbs anyway since we won't be able to send the buffer as
> the user requested.
> 
> 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>

Applied to net-next
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Patch

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 0c7321c..bde0dec 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -195,6 +195,19 @@  static struct sk_buff *page_to_skb(struct virtnet_info *vi,
 	len -= copy;
 	offset += copy;
 
+	/*
+	 * Verify that we can indeed put this data into a skb.
+	 * This is here to handle cases when the device erroneously
+	 * tries to receive more than is possible. This is usually
+	 * the case of a broken device.
+	 */
+	if (unlikely(len > MAX_SKB_FRAGS * PAGE_SIZE)) {
+		if (net_ratelimit())
+			pr_debug("%s: too much data\n", skb->dev->name);
+		dev_kfree_skb(skb);
+		return NULL;
+	}
+
 	while (len) {
 		set_skb_frag(skb, page, offset, &len);
 		page = (struct page *)page->private;