af_packet: Don't use skb after dev_queue_xmit()

tpacket_snd() can change and kfree an skb after dev_queue_xmit(),
which is illegal.

With debugging by: Stephen Hemminger <shemminger@vyatta.com>

Reported-by: Michael Breuer <mbreuer@majjas.com>
With help from: David S. Miller <davem@davemloft.net>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Tested-by: Michael Breuer<mbreuer@majjas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 5 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index e0516a22be2e..f126d18dbdc4 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1021,8 +1021,20 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
 
                 status = TP_STATUS_SEND_REQUEST;
                 err = dev_queue_xmit(skb);
-                if (unlikely(err > 0 && (err = net_xmit_errno(err)) != 0))
-                        goto out_xmit;
+                if (unlikely(err > 0)) {
+                        err = net_xmit_errno(err);
+                        if (err && __packet_get_status(po, ph) ==
+                                   TP_STATUS_AVAILABLE) {
+                                /* skb was destructed already */
+                                skb = NULL;
+                                goto out_status;
+                        }
+                        /*
+                         * skb was dropped but not destructed yet;
+                         * let's treat it like congestion or err < 0
+                         */
+                        err = 0;
+                }
                 packet_increment_head(&po->tx_ring);
                 len_sum += tp_len;
         } while (likely((ph != NULL) ||
@@ -1033,9 +1045,6 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
         err = len_sum;
         goto out_put;
 
-out_xmit:
-        skb->destructor = sock_wfree;
-        atomic_dec(&po->tx_ring.pending);
 out_status:
         __packet_set_status(po, ph, status);
         kfree_skb(skb);