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:

quoted

On Wed, Sep 28, 2011 at 05:40:54PM +0300, Sasha Levin wrote:

quoted

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 <redacted>
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 <redacted>
---
 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.