ravb: Fix use-after-free ravb_tstamp_skb

When a Tx timestamp is requested, a pointer to the skb is stored in the
ravb_tstamp_skb struct. This was done without an skb_get. There exists
the possibility that the skb could be freed by ravb_tx_free (when
ravb_tx_free is called from ravb_start_xmit) before the timestamp was
processed, leading to a use-after-free bug.

Use skb_get when filling a ravb_tstamp_skb struct, and add appropriate
frees/consumes when a ravb_tstamp_skb struct is freed.

Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper")
Signed-off-by: Tho Vu <tho.vu.wh@rvc.renesas.com>
Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index ef8f08931fe8..6cacd5e893ac 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Renesas Ethernet AVB device driver
  *
- * Copyright (C) 2014-2015 Renesas Electronics Corporation
+ * Copyright (C) 2014-2019 Renesas Electronics Corporation
  * Copyright (C) 2015 Renesas Solutions Corp.
  * Copyright (C) 2015-2016 Cogent Embedded, Inc. <source@cogentembedded.com>
  *
@@ -513,7 +513,10 @@ static void ravb_get_tx_tstamp(struct net_device *ndev)
                         kfree(ts_skb);
                         if (tag == tfa_tag) {
                                 skb_tstamp_tx(skb, &shhwtstamps);
+                                dev_consume_skb_any(skb);
                                 break;
+                        } else {
+                                dev_kfree_skb_any(skb);
                         }
                 }
                 ravb_modify(ndev, TCCR, TCCR_TFR, TCCR_TFR);
@@ -1564,7 +1567,7 @@ static netdev_tx_t ravb_start_xmit(struct sk_buff *skb, struct net_device *ndev)
                         }
                         goto unmap;
                 }
-                ts_skb->skb = skb;
+                ts_skb->skb = skb_get(skb);
                 ts_skb->tag = priv->ts_skb_tag++;
                 priv->ts_skb_tag &= 0x3ff;
                 list_add_tail(&ts_skb->list, &priv->ts_skb_list);
@@ -1693,6 +1696,7 @@ static int ravb_close(struct net_device *ndev)
         /* Clear the timestamp list */
         list_for_each_entry_safe(ts_skb, ts_skb2, &priv->ts_skb_list, list) {
                 list_del(&ts_skb->list);
+                kfree_skb(ts_skb->skb);
                 kfree(ts_skb);
         }