linux-kernel - [011/140] veth: Dont kfree_skb() after dev_forward

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Date:	Fri, 30 Jul 2010 10:29:36 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Eric Dumazet <eric.dumazet@...il.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [011/140] veth: Dont kfree_skb() after dev_forward_skb()

2.6.33-stable review patch.  If anyone has any objections, please let us know.

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


From: Eric Dumazet <eric.dumazet@...il.com>

[ Upstream commit 6ec82562ffc6f297d0de36d65776cff8e5704867 ]

In case of congestion, netif_rx() frees the skb, so we must assume
dev_forward_skb() also consume skb.

Bug introduced by commit 445409602c092
(veth: move loopback logic to common location)

We must change dev_forward_skb() to always consume skb, and veth to not
double free it.

Bug report : http://marc.info/?l=linux-netdev&m=127310770900442&w=3

Reported-by: Martín Ferrari <martin.ferrari@...il.com>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 drivers/net/veth.c |    1 -
 net/core/dev.c     |   10 +++++-----
 2 files changed, 5 insertions(+), 6 deletions(-)

--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -186,7 +186,6 @@ tx_drop:
 	return NETDEV_TX_OK;
 
 rx_drop:
-	kfree_skb(skb);
 	rcv_stats->rx_dropped++;
 	return NETDEV_TX_OK;
 }
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1428,7 +1428,7 @@ static inline void net_timestamp(struct
  *
  * return values:
  *	NET_RX_SUCCESS	(no congestion)
- *	NET_RX_DROP     (packet was dropped)
+ *	NET_RX_DROP     (packet was dropped, but freed)
  *
  * dev_forward_skb can be used for injecting an skb from the
  * start_xmit function of one device into the receive queue
@@ -1442,11 +1442,11 @@ int dev_forward_skb(struct net_device *d
 {
 	skb_orphan(skb);
 
-	if (!(dev->flags & IFF_UP))
-		return NET_RX_DROP;
-
-	if (skb->len > (dev->mtu + dev->hard_header_len))
+	if (!(dev->flags & IFF_UP) ||
+	    (skb->len > (dev->mtu + dev->hard_header_len))) {
+		kfree_skb(skb);
 		return NET_RX_DROP;
+	}
 
 	skb_dst_drop(skb);
 	skb->tstamp.tv64 = 0;


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