[PATCH 4.9 35/54] macsec: avoid use-after-free in macsec_handle_frame()

[Greg Kroah-Hartman]

From: Eric Dumazet <edumazet@xxxxxxxxxx>

commit c7cc9200e9b4a2ac172e990ef1975cd42975dad6 upstream.

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@xxxxxxxxxx>
Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
Acked-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/net/macsec.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -1087,6 +1087,7 @@ static rx_handler_result_t macsec_handle
 	struct macsec_rx_sa *rx_sa;
 	struct macsec_rxh_data *rxd;
 	struct macsec_dev *macsec;
+	unsigned int len;
 	sci_t sci;
 	u32 pn;
 	bool cbit;
@@ -1242,9 +1243,10 @@ deliver:
 	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++;