tun: Fix use-after-free on XDP_TX

On XDP_TX we need to free up the frame only when tun_xdp_tx() returns a
negative value. A positive value indicates that the packet is
successfully enqueued to the ptr_ring, so freeing the page causes
use-after-free.

Fixes: fa294a2aac19 ("xdp: change ndo_xdp_xmit API to support bulking")
Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index a192a017cc68878360505b93df151de3d0b9b730..f5727baac84a5d10fd70837a75fcfa8194992f9a 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1688,7 +1688,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
                case XDP_TX:
                        get_page(alloc_frag->page);
                        alloc_frag->offset += buflen;
-                       if (tun_xdp_tx(tun->dev, &xdp))
+                       if (tun_xdp_tx(tun->dev, &xdp) < 0)
                                goto err_redirect;
                        rcu_read_unlock();
                        local_bh_enable();