Subject: [PATCH AUTOSEL 4.4 11/15] ravb: Fix use-after-free ravb_tstamp_skb

From: Sasha Levin <[email-masked]>
Date: Thu, 29 Aug 2019 14:17:58 -0400

From: Tho Vu <[email-masked]>

[ Upstream commit cfef46d692efd852a0da6803f920cc756eea2855 ]

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 <[email-masked]>
Signed-off-by: Kazuya Mizuguchi <[email-masked]>
Signed-off-by: Simon Horman <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
Signed-off-by: Sasha Levin <[email-masked]>
---
 drivers/net/ethernet/renesas/ravb_main.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 29d31eb995d7f..fedfd94699cb8 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -1,6 +1,6 @@
 /* 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 Cogent Embedded, Inc. <[email-masked]>
  *
@@ -501,7 +501,10 @@ 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_write(ndev, ravb_read(ndev, TCCR) | TCCR_TFR, TCCR);
@@ -1382,7 +1385,7 @@ static netdev_tx_t ravb_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 					 DMA_TO_DEVICE);
 			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);
@@ -1514,6 +1517,7 @@ 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);
 	}
 
-- 
2.20.1