netdev - [PATCH net] macsec: avoid use-after-free in macsec_handle

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Date:   Wed,  7 Oct 2020 01:42:46 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH net] macsec: avoid use-after-free in macsec_handle_frame()

From: Eric Dumazet <edumazet@...gle.com>

De-referencing skb after call to gro_cells_receive() is not allowed.
We need to fetch skb->len earlier.

Fixes: 5491e7c6b1a9 ("macsec: enable GRO and RPS on macsec devices")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Paolo Abeni <pabeni@...hat.com>
---
 drivers/net/macsec.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index 9159846b8b9388644bcf8f136231726d8cf297f2..787ac2c8e74ebef65534291aacb6dc5d9b839b27 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -1077,6 +1077,7 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
 	struct macsec_rx_sa *rx_sa;
 	struct macsec_rxh_data *rxd;
 	struct macsec_dev *macsec;
+	unsigned int len;
 	sci_t sci;
 	u32 hdr_pn;
 	bool cbit;
@@ -1232,9 +1233,10 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
 	macsec_rxsc_put(rx_sc);
 
 	skb_orphan(skb);
+	len = skb->len;
 	ret = gro_cells_receive(&macsec->gro_cells, skb);
 	if (ret == NET_RX_SUCCESS)
-		count_rx(dev, skb->len);
+		count_rx(dev, len);
 	else
 		macsec->secy.netdev->stats.rx_dropped++;
 
-- 
2.28.0.806.g8561365e88-goog