netdev - [PATCH] net: fec: fix potential use after free

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Message-ID: <1387479182.19078.369.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Thu, 19 Dec 2013 10:53:02 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>, Frank Li <Frank.Li@...escale.com>,
	Richard Cochran <richardcochran@...il.com>
Subject: [PATCH] net: fec: fix potential use after free

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

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.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Fixes: de5fb0a05348 ("net: fec: put tx to napi poll function to fix dead lock")
Cc: Frank Li <Frank.Li@...escale.com>
Cc: Richard Cochran <richardcochran@...il.com>
---
 drivers/net/ethernet/freescale/fec_main.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index e7c8b749c5a5..50bb71c663e2 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -428,6 +428,8 @@ fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	/* If this was the last BD in the ring, start at the beginning again. */
 	bdp = fec_enet_get_nextdesc(bdp, fep);
 
+	skb_tx_timestamp(skb);
+
 	fep->cur_tx = bdp;
 
 	if (fep->cur_tx == fep->dirty_tx)
@@ -436,8 +438,6 @@ fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	/* Trigger transmission start */
 	writel(0, fep->hwp + FEC_X_DES_ACTIVE);
 
-	skb_tx_timestamp(skb);
-
 	return NETDEV_TX_OK;
 }
 


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