[PATCH 3.12 29/77] arc_emac: fix potential use after free

[Greg Kroah-Hartman]

3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <eric.dumazet@xxxxxxxxx>

[ Upstream commit 37ec274e9713eafc2ba6c4471420f06cb8f68ecf ]

Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>

skb_tx_timestamp(skb) should be called _before_ TX completion
has a chance to trigger, otherwise it is too late and we access
freed memory.

Fixes: e4f2379db6c6 ("ethernet/arc/arc_emac - Add new driver")
From: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Alexey Brodkin <Alexey.Brodkin@xxxxxxxxxxxx>
Cc: Richard Cochran <richardcochran@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/ethernet/arc/emac_main.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/arc/emac_main.c
+++ b/drivers/net/ethernet/arc/emac_main.c
@@ -565,6 +565,8 @@ static int arc_emac_tx(struct sk_buff *s
 	/* Make sure pointer to data buffer is set */
 	wmb();
 
+	skb_tx_timestamp(skb);
+
 	*info = cpu_to_le32(FOR_EMAC | FIRST_OR_LAST_MASK | len);
 
 	/* Increment index to point to the next BD */
@@ -579,8 +581,6 @@ static int arc_emac_tx(struct sk_buff *s
 
 	arc_reg_set(priv, R_STATUS, TXPL_MASK);
 
-	skb_tx_timestamp(skb);
-
 	return NETDEV_TX_OK;
 }
 


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