virtio-net: Add validation for used length

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

Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210531135852.113-1-xieyongji@bytedance.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 073fec4..ed969b6 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -730,6 +730,12 @@ static struct sk_buff *receive_small(struct net_device *dev,
        len -= vi->hdr_len;
        stats->bytes += len;
 
+       if (unlikely(len > GOOD_PACKET_LEN)) {
+               pr_debug("%s: rx error: len %u exceeds max size %d\n",
+                        dev->name, len, GOOD_PACKET_LEN);
+               dev->stats.rx_length_errors++;
+               goto err_len;
+       }
        rcu_read_lock();
        xdp_prog = rcu_dereference(rq->xdp_prog);
        if (xdp_prog) {
@@ -833,6 +839,7 @@ err:
 err_xdp:
        rcu_read_unlock();
        stats->xdp_drops++;
+err_len:
        stats->drops++;
        put_page(page);
 xdp_xmit:
@@ -886,6 +893,12 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
        head_skb = NULL;
        stats->bytes += len - vi->hdr_len;
 
+       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_skb;
+       }
        rcu_read_lock();
        xdp_prog = rcu_dereference(rq->xdp_prog);
        if (xdp_prog) {
@@ -1012,13 +1025,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
        }
        rcu_read_unlock();
 
-       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_skb;
-       }
-
        head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog,
                               metasize, !!headroom);
        curr_skb = head_skb;