[PATCH] virtio-net: Add validation for used length

[Xie Yongji]

This adds validation for used length (might come
from an untrusted device) to avoid data corruption
or loss.

Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
---
 drivers/net/virtio_net.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index c4711e23af88..2dcdc1a3c7e8 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -668,6 +668,13 @@ static struct sk_buff *receive_small(struct net_device *dev,
 		void *orig_data;
 		u32 act;
 
+		if (unlikely(len > GOOD_PACKET_LEN)) {
+			pr_debug("%s: rx error: len %u exceeds max size %lu\n",
+				 dev->name, len, GOOD_PACKET_LEN);
+			dev->stats.rx_length_errors++;
+			goto err_xdp;
+		}
+
 		if (unlikely(hdr->hdr.gso_type))
 			goto err_xdp;
 
@@ -739,6 +746,14 @@ static struct sk_buff *receive_small(struct net_device *dev,
 	}
 	rcu_read_unlock();
 
+	if (unlikely(len > GOOD_PACKET_LEN)) {
+		pr_debug("%s: rx error: len %u exceeds max size %lu\n",
+			 dev->name, len, GOOD_PACKET_LEN);
+		dev->stats.rx_length_errors++;
+		put_page(page);
+		return NULL;
+	}
+
 	skb = build_skb(buf, buflen);
 	if (!skb) {
 		put_page(page);
@@ -822,6 +837,13 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 		void *data;
 		u32 act;
 
+		if (unlikely(len > truesize)) {
+			pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
+				 dev->name, len, (unsigned long)ctx);
+			dev->stats.rx_length_errors++;
+			goto err_xdp;
+		}
+
 		/* Transient failure which in theory could occur if
 		 * in-flight packets from before XDP was enabled reach
 		 * the receive path after XDP is loaded.
-- 
2.11.0