[PATCH stable 0/2] virtio-net: backport error handling bugfix

[PATCH stable 0/2] virtio-net: backport error handling bugfix

[Michael S. Tsirkin]

Error handling for virtio-net mergeable buffers was broken
for a long time. Backport recent bugfix to a stable
kernel.

Please note that it's really a single patch split out in two for ease of
review: if we apply 1/2 only the code is correct but ugly and confusing, so I
think it's best to backport both patches 1/2 and 2/2 same as upstream has them.

Please review and consider for stable.

Michael S. Tsirkin (2):
  virtio_net: fix error handling for mergeable buffers
  virtio-net: make all RX paths handle erors consistently

 drivers/net/virtio_net.c | 103 ++++++++++++++++++++++++++++++++++-------------
 1 file changed, 74 insertions(+), 29 deletions(-)

-- 
MST

[PATCH stable 1/2] virtio_net: fix error handling for mergeable buffers

[Michael S. Tsirkin]

Eric Dumazet noticed that if we encounter an error
when processing a mergeable buffer, we don't
dequeue all of the buffers from this packet,
the result is almost sure to be loss of networking.

Jason Wang noticed that we also leak a page and that we don't decrement
the rq buf count, so we won't repost buffers (a resource leak).

Fix both issues.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Michael Dalton <mwdalton@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: David S. Miller <davem@davemloft.net>

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

(cherry picked from commit 8fc3b9e9a229778e5af3aa453c44f1a3857ba769)
---
 drivers/net/virtio_net.c | 66 +++++++++++++++++++++++++++++++++---------------
 1 file changed, 46 insertions(+), 20 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 9fbdfcd..435076f 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -297,26 +297,33 @@ static struct sk_buff *page_to_skb(struct receive_queue *rq,
 	return skb;
 }
 
-static int receive_mergeable(struct receive_queue *rq, struct sk_buff *skb)
+static struct sk_buff *receive_mergeable(struct net_device *dev,
+					 struct receive_queue *rq,
+					 void *buf,
+					 unsigned int len)
 {
-	struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
-	struct page *page;
-	int num_buf, i, len;
+	struct skb_vnet_hdr *hdr = page_address(buf);
+	int num_buf = hdr->mhdr.num_buffers;
+	struct page *page = buf;
+	struct sk_buff *skb = page_to_skb(rq, page, len);
+	int i;
+
+	if (unlikely(!skb))
+		goto err_skb;
 
-	num_buf = hdr->mhdr.num_buffers;
 	while (--num_buf) {
 		i = skb_shinfo(skb)->nr_frags;
 		if (i >= MAX_SKB_FRAGS) {
 			pr_debug("%s: packet too long\n", skb->dev->name);
 			skb->dev->stats.rx_length_errors++;
-			return -EINVAL;
+			return NULL;
 		}
 		page = virtqueue_get_buf(rq->vq, &len);
 		if (!page) {
-			pr_debug("%s: rx error: %d buffers missing\n",
-				 skb->dev->name, hdr->mhdr.num_buffers);
-			skb->dev->stats.rx_length_errors++;
-			return -EINVAL;
+			pr_debug("%s: rx error: %d buffers %d missing\n",
+				 dev->name, hdr->mhdr.num_buffers, num_buf);
+			dev->stats.rx_length_errors++;
+			goto err_buf;
 		}
 
 		if (len > PAGE_SIZE)
@@ -326,7 +333,25 @@ static int receive_mergeable(struct receive_queue *rq, struct sk_buff *skb)
 
 		--rq->num;
 	}
-	return 0;
+	return skb;
+err_skb:
+	give_pages(rq, page);
+	while (--num_buf) {
+		buf = virtqueue_get_buf(rq->vq, &len);
+		if (unlikely(!buf)) {
+			pr_debug("%s: rx error: %d buffers missing\n",
+				 dev->name, num_buf);
+			dev->stats.rx_length_errors++;
+			break;
+		}
+		page = buf;
+		give_pages(rq, page);
+		--rq->num;
+	}
+err_buf:
+	dev->stats.rx_dropped++;
+	dev_kfree_skb(skb);
+	return NULL;
 }
 
 static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
@@ -354,17 +379,18 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
 		skb_trim(skb, len);
 	} else {
 		page = buf;
-		skb = page_to_skb(rq, page, len);
-		if (unlikely(!skb)) {
-			dev->stats.rx_dropped++;
-			give_pages(rq, page);
-			return;
-		}
-		if (vi->mergeable_rx_bufs)
-			if (receive_mergeable(rq, skb)) {
-				dev_kfree_skb(skb);
+		if (vi->mergeable_rx_bufs) {
+			skb = receive_mergeable(dev, rq, page, len);
+			if (unlikely(!skb))
+				return;
+		} else {
+			skb = page_to_skb(rq, page, len);
+			if (unlikely(!skb)) {
+				dev->stats.rx_dropped++;
+				give_pages(rq, page);
 				return;
 			}
+		}
 	}
 
 	hdr = skb_vnet_hdr(skb);
-- 
MST

Re: [PATCH stable 1/2] virtio_net: fix error handling for mergeable buffers

[Michael Dalton]

Hi Michael, quick question below:

On Wed, Dec 25, 2013 at 6:56 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
>                 if (i >= MAX_SKB_FRAGS) {
>                         pr_debug("%s: packet too long\n", skb->dev->name);
>                         skb->dev->stats.rx_length_errors++;
> -                       return -EINVAL;
> +                       return NULL;
>                 }

Should this error handling path free the SKB before returning NULL?
It seems like if we just return NULL we may leak memory.

Best,

Mike

Re: [PATCH stable 1/2] virtio_net: fix error handling for mergeable buffers

[Michael S. Tsirkin]

On Wed, Dec 25, 2013 at 10:33:37AM -0800, Michael Dalton wrote:
> Hi Michael, quick question below:
> 
> On Wed, Dec 25, 2013 at 6:56 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> >                 if (i >= MAX_SKB_FRAGS) {
> >                         pr_debug("%s: packet too long\n", skb->dev->name);
> >                         skb->dev->stats.rx_length_errors++;
> > -                       return -EINVAL;
> > +                       return NULL;
> >                 }
> 
> Should this error handling path free the SKB before returning NULL?
> It seems like if we just return NULL we may leak memory.
> 
> Best,
> 
> Mike

It's a device error, but
I agree, if we touch this code anyway there's no reason not to handle
this consistently and do goto toward end of file.
It's not a backport anymore though - this code is gone upstream,
so I'll make it a separate patch I think.

-- 
MST

Re: [PATCH stable 1/2] virtio_net: fix error handling for mergeable buffers

[Michael Dalton]

Acked-by: Michael Dalton <mwdalton@google.com>

Re: [PATCH stable 1/2] virtio_net: fix error handling for mergeable buffers

[Jason Wang]

On 12/25/2013 10:56 PM, Michael S. Tsirkin wrote:
> Eric Dumazet noticed that if we encounter an error
> when processing a mergeable buffer, we don't
> dequeue all of the buffers from this packet,
> the result is almost sure to be loss of networking.
>
> Jason Wang noticed that we also leak a page and that we don't decrement
> the rq buf count, so we won't repost buffers (a resource leak).

This issue does not existed in stable tree.
> Fix both issues.
>
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> Cc: Michael Dalton <mwdalton@google.com>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: David S. Miller <davem@davemloft.net>
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>
> (cherry picked from commit 8fc3b9e9a229778e5af3aa453c44f1a3857ba769)
> ---
>  drivers/net/virtio_net.c | 66 +++++++++++++++++++++++++++++++++---------------
>  1 file changed, 46 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 9fbdfcd..435076f 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -297,26 +297,33 @@ static struct sk_buff *page_to_skb(struct receive_queue *rq,
>  	return skb;
>  }
>  
> -static int receive_mergeable(struct receive_queue *rq, struct sk_buff *skb)
> +static struct sk_buff *receive_mergeable(struct net_device *dev,
> +					 struct receive_queue *rq,
> +					 void *buf,
> +					 unsigned int len)
>  {
> -	struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
> -	struct page *page;
> -	int num_buf, i, len;
> +	struct skb_vnet_hdr *hdr = page_address(buf);
> +	int num_buf = hdr->mhdr.num_buffers;
> +	struct page *page = buf;
> +	struct sk_buff *skb = page_to_skb(rq, page, len);
> +	int i;
> +
> +	if (unlikely(!skb))
> +		goto err_skb;
>  
> -	num_buf = hdr->mhdr.num_buffers;
>  	while (--num_buf) {
>  		i = skb_shinfo(skb)->nr_frags;
>  		if (i >= MAX_SKB_FRAGS) {
>  			pr_debug("%s: packet too long\n", skb->dev->name);
>  			skb->dev->stats.rx_length_errors++;
> -			return -EINVAL;
> +			return NULL;
>  		}
>  		page = virtqueue_get_buf(rq->vq, &len);
>  		if (!page) {
> -			pr_debug("%s: rx error: %d buffers missing\n",
> -				 skb->dev->name, hdr->mhdr.num_buffers);
> -			skb->dev->stats.rx_length_errors++;
> -			return -EINVAL;
> +			pr_debug("%s: rx error: %d buffers %d missing\n",
> +				 dev->name, hdr->mhdr.num_buffers, num_buf);
> +			dev->stats.rx_length_errors++;
> +			goto err_buf;
>  		}
>  
>  		if (len > PAGE_SIZE)
> @@ -326,7 +333,25 @@ static int receive_mergeable(struct receive_queue *rq, struct sk_buff *skb)
>  
>  		--rq->num;
>  	}
> -	return 0;
> +	return skb;
> +err_skb:
> +	give_pages(rq, page);
> +	while (--num_buf) {
> +		buf = virtqueue_get_buf(rq->vq, &len);
> +		if (unlikely(!buf)) {
> +			pr_debug("%s: rx error: %d buffers missing\n",
> +				 dev->name, num_buf);
> +			dev->stats.rx_length_errors++;
> +			break;
> +		}
> +		page = buf;
> +		give_pages(rq, page);
> +		--rq->num;
> +	}
> +err_buf:
> +	dev->stats.rx_dropped++;
> +	dev_kfree_skb(skb);
> +	return NULL;
>  }
>  
>  static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
> @@ -354,17 +379,18 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
>  		skb_trim(skb, len);
>  	} else {
>  		page = buf;
> -		skb = page_to_skb(rq, page, len);
> -		if (unlikely(!skb)) {
> -			dev->stats.rx_dropped++;
> -			give_pages(rq, page);
> -			return;
> -		}
> -		if (vi->mergeable_rx_bufs)
> -			if (receive_mergeable(rq, skb)) {
> -				dev_kfree_skb(skb);
> +		if (vi->mergeable_rx_bufs) {
> +			skb = receive_mergeable(dev, rq, page, len);
> +			if (unlikely(!skb))
> +				return;
> +		} else {
> +			skb = page_to_skb(rq, page, len);
> +			if (unlikely(!skb)) {
> +				dev->stats.rx_dropped++;
> +				give_pages(rq, page);
>  				return;
>  			}
> +		}
>  	}
>  
>  	hdr = skb_vnet_hdr(skb);

[PATCH stable 2/2] virtio-net: make all RX paths handle erors consistently

[Michael S. Tsirkin]

receive mergeable now handles errors internally.
Do same for big and small packet paths, otherwise
the logic is too hard to follow.

Cc: Jason Wang <jasowang@redhat.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

(cherry picked from commit f121159d72091f25afb22007c833e60a6845e912)
---
 drivers/net/virtio_net.c | 56 +++++++++++++++++++++++++++++++-----------------
 1 file changed, 36 insertions(+), 20 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 435076f..c0ed6d5 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -297,6 +297,34 @@ static struct sk_buff *page_to_skb(struct receive_queue *rq,
 	return skb;
 }
 
+static struct sk_buff *receive_small(void *buf, unsigned int len)
+{
+	struct sk_buff * skb = buf;
+
+	len -= sizeof(struct virtio_net_hdr);
+	skb_trim(skb, len);
+
+	return skb;
+}
+
+static struct sk_buff *receive_big(struct net_device *dev,
+				   struct receive_queue *rq,
+				   void *buf)
+{
+	struct page *page = buf;
+	struct sk_buff *skb = page_to_skb(rq, page, 0);
+
+	if (unlikely(!skb))
+		goto err;
+
+	return skb;
+
+err:
+	dev->stats.rx_dropped++;
+	give_pages(rq, page);
+	return NULL;
+}
+
 static struct sk_buff *receive_mergeable(struct net_device *dev,
 					 struct receive_queue *rq,
 					 void *buf,
@@ -360,7 +388,6 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
 	struct net_device *dev = vi->dev;
 	struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
 	struct sk_buff *skb;
-	struct page *page;
 	struct skb_vnet_hdr *hdr;
 
 	if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
@@ -372,26 +399,15 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
 			dev_kfree_skb(buf);
 		return;
 	}
+	if (vi->mergeable_rx_bufs)
+		skb = receive_mergeable(dev, rq, buf, len);
+	else if (vi->big_packets)
+		skb = receive_big(dev, rq, buf);
+	else
+		skb = receive_small(buf, len);
 
-	if (!vi->mergeable_rx_bufs && !vi->big_packets) {
-		skb = buf;
-		len -= sizeof(struct virtio_net_hdr);
-		skb_trim(skb, len);
-	} else {
-		page = buf;
-		if (vi->mergeable_rx_bufs) {
-			skb = receive_mergeable(dev, rq, page, len);
-			if (unlikely(!skb))
-				return;
-		} else {
-			skb = page_to_skb(rq, page, len);
-			if (unlikely(!skb)) {
-				dev->stats.rx_dropped++;
-				give_pages(rq, page);
-				return;
-			}
-		}
-	}
+	if (unlikely(!skb))
+		return;
 
 	hdr = skb_vnet_hdr(skb);
 
-- 
MST

Re: [PATCH stable 2/2] virtio-net: make all RX paths handle erors consistently

[Jason Wang]

On 12/25/2013 10:56 PM, Michael S. Tsirkin wrote:
> receive mergeable now handles errors internally.
> Do same for big and small packet paths, otherwise
> the logic is too hard to follow.
>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: David S. Miller <davem@davemloft.net>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>
> (cherry picked from commit f121159d72091f25afb22007c833e60a6845e912)
> ---
>  drivers/net/virtio_net.c | 56 +++++++++++++++++++++++++++++++-----------------
>  1 file changed, 36 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 435076f..c0ed6d5 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -297,6 +297,34 @@ static struct sk_buff *page_to_skb(struct receive_queue *rq,
>  	return skb;
>  }
>  
> +static struct sk_buff *receive_small(void *buf, unsigned int len)
> +{
> +	struct sk_buff * skb = buf;
> +
> +	len -= sizeof(struct virtio_net_hdr);
> +	skb_trim(skb, len);
> +
> +	return skb;
> +}
> +
> +static struct sk_buff *receive_big(struct net_device *dev,
> +				   struct receive_queue *rq,
> +				   void *buf)
> +{
> +	struct page *page = buf;
> +	struct sk_buff *skb = page_to_skb(rq, page, 0);
> +
> +	if (unlikely(!skb))
> +		goto err;
> +
> +	return skb;
> +
> +err:
> +	dev->stats.rx_dropped++;
> +	give_pages(rq, page);
> +	return NULL;
> +}
> +
>  static struct sk_buff *receive_mergeable(struct net_device *dev,
>  					 struct receive_queue *rq,
>  					 void *buf,
> @@ -360,7 +388,6 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
>  	struct net_device *dev = vi->dev;
>  	struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
>  	struct sk_buff *skb;
> -	struct page *page;
>  	struct skb_vnet_hdr *hdr;
>  
>  	if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
> @@ -372,26 +399,15 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
>  			dev_kfree_skb(buf);
>  		return;
>  	}
> +	if (vi->mergeable_rx_bufs)
> +		skb = receive_mergeable(dev, rq, buf, len);
> +	else if (vi->big_packets)
> +		skb = receive_big(dev, rq, buf);
> +	else
> +		skb = receive_small(buf, len);
>  
> -	if (!vi->mergeable_rx_bufs && !vi->big_packets) {
> -		skb = buf;
> -		len -= sizeof(struct virtio_net_hdr);
> -		skb_trim(skb, len);
> -	} else {
> -		page = buf;
> -		if (vi->mergeable_rx_bufs) {
> -			skb = receive_mergeable(dev, rq, page, len);
> -			if (unlikely(!skb))
> -				return;
> -		} else {
> -			skb = page_to_skb(rq, page, len);
> -			if (unlikely(!skb)) {
> -				dev->stats.rx_dropped++;
> -				give_pages(rq, page);
> -				return;
> -			}
> -		}
> -	}
> +	if (unlikely(!skb))
> +		return;
>  
>  	hdr = skb_vnet_hdr(skb);
>  
Ack-ed by: Jason Wang <jasowang@redhat.com>

Re: [PATCH stable 2/2] virtio-net: make all RX paths handle erors consistently

[Zhi Yong Wu]

typo in the subject....

s/erors/errors/

On Wed, Dec 25, 2013 at 10:56 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> receive mergeable now handles errors internally.
> Do same for big and small packet paths, otherwise
> the logic is too hard to follow.
>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: David S. Miller <davem@davemloft.net>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>
> (cherry picked from commit f121159d72091f25afb22007c833e60a6845e912)
> ---
>  drivers/net/virtio_net.c | 56 +++++++++++++++++++++++++++++++-----------------
>  1 file changed, 36 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 435076f..c0ed6d5 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -297,6 +297,34 @@ static struct sk_buff *page_to_skb(struct receive_queue *rq,
>         return skb;
>  }
>
> +static struct sk_buff *receive_small(void *buf, unsigned int len)
> +{
> +       struct sk_buff * skb = buf;
> +
> +       len -= sizeof(struct virtio_net_hdr);
> +       skb_trim(skb, len);
> +
> +       return skb;
> +}
> +
> +static struct sk_buff *receive_big(struct net_device *dev,
> +                                  struct receive_queue *rq,
> +                                  void *buf)
> +{
> +       struct page *page = buf;
> +       struct sk_buff *skb = page_to_skb(rq, page, 0);
> +
> +       if (unlikely(!skb))
> +               goto err;
> +
> +       return skb;
> +
> +err:
> +       dev->stats.rx_dropped++;
> +       give_pages(rq, page);
> +       return NULL;
> +}
> +
>  static struct sk_buff *receive_mergeable(struct net_device *dev,
>                                          struct receive_queue *rq,
>                                          void *buf,
> @@ -360,7 +388,6 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
>         struct net_device *dev = vi->dev;
>         struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
>         struct sk_buff *skb;
> -       struct page *page;
>         struct skb_vnet_hdr *hdr;
>
>         if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
> @@ -372,26 +399,15 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
>                         dev_kfree_skb(buf);
>                 return;
>         }
> +       if (vi->mergeable_rx_bufs)
> +               skb = receive_mergeable(dev, rq, buf, len);
> +       else if (vi->big_packets)
> +               skb = receive_big(dev, rq, buf);
> +       else
> +               skb = receive_small(buf, len);
>
> -       if (!vi->mergeable_rx_bufs && !vi->big_packets) {
> -               skb = buf;
> -               len -= sizeof(struct virtio_net_hdr);
> -               skb_trim(skb, len);
> -       } else {
> -               page = buf;
> -               if (vi->mergeable_rx_bufs) {
> -                       skb = receive_mergeable(dev, rq, page, len);
> -                       if (unlikely(!skb))
> -                               return;
> -               } else {
> -                       skb = page_to_skb(rq, page, len);
> -                       if (unlikely(!skb)) {
> -                               dev->stats.rx_dropped++;
> -                               give_pages(rq, page);
> -                               return;
> -                       }
> -               }
> -       }
> +       if (unlikely(!skb))
> +               return;
>
>         hdr = skb_vnet_hdr(skb);
>
> --
> MST
>
> _______________________________________________
> Virtualization mailing list
> Virtualization@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/virtualization



-- 
Regards,

Zhi Yong Wu

[PATCH stable] virtio_net: don't leak memory or block when too many frags

[Michael S. Tsirkin]

We leak an skb when there are too many frags,
we also stop processing the packet in the middle,
the result is almost sure to be loss of networking.

Reported-by: Michael Dalton <mwdalton@google.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

Note: this path is gone upstream, so this patch is
for stable kernel only.
This is on top of series:
	virtio-net: backport error handling bugfix
that I sent previously (and that this is in reply to).

 drivers/net/virtio_net.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index c0ed6d5..86fe1e7 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -344,7 +344,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 		if (i >= MAX_SKB_FRAGS) {
 			pr_debug("%s: packet too long\n", skb->dev->name);
 			skb->dev->stats.rx_length_errors++;
-			return NULL;
+			goto err_frags;
 		}
 		page = virtqueue_get_buf(rq->vq, &len);
 		if (!page) {
@@ -364,6 +364,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 	return skb;
 err_skb:
 	give_pages(rq, page);
 	while (--num_buf) {
+err_frags:
 		buf = virtqueue_get_buf(rq->vq, &len);
 		if (unlikely(!buf)) {
-- 
MST

Re: [PATCH stable] virtio_net: don't leak memory or block when too many frags

[Michael Dalton]

Acked-by: Michael Dalton <mwdalton@google.com>