netdev - Re: [PATCH] gainfar.c : skb_over

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Date:	Thu, 17 Jun 2010 12:20:30 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	liberty@...ricom.com
Cc:	galak@...nel.crashing.org, netdev@...r.kernel.org
Subject: Re: [PATCH] gainfar.c : skb_over_panic

From: Eran Liberty <liberty@...ricom.com>
Date: Thu, 17 Jun 2010 19:32:54 +0300

> I have demonstrated skb_over_panic with linux 2.6.32.15 on a mpc8548
> based product.

A fix for a similar bug was necessary for the ucc_geth driver,
see below.

The real problem is that skb->data assignment, the rest of the
SKB state has to be reset, and not doing that is what results in
the skb_over_panic calls.

>From db176edc89abbf22e6db6853f8581f9475fe8ec1 Mon Sep 17 00:00:00 2001
From: Sergey Matyukevich <geomatsi@...il.com>
Date: Mon, 14 Jun 2010 06:35:20 +0000
Subject: [PATCH] ucc_geth: fix for RX skb buffers recycling

This patch implements a proper modification of RX skb buffers before
recycling. Adjusting only skb->data is not enough because after that
skb->tail and skb->len become incorrect.

Signed-off-by: Sergey Matyukevich <geomatsi@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
---
 drivers/net/ucc_geth.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/net/ucc_geth.c b/drivers/net/ucc_geth.c
index 4a34833..807470e 100644
--- a/drivers/net/ucc_geth.c
+++ b/drivers/net/ucc_geth.c
@@ -3215,6 +3215,8 @@ static int ucc_geth_rx(struct ucc_geth_private *ugeth, u8 rxQ, int rx_work_limit
 					   __func__, __LINE__, (u32) skb);
 			if (skb) {
 				skb->data = skb->head + NET_SKB_PAD;
+				skb->len = 0;
+				skb_reset_tail_pointer(skb);
 				__skb_queue_head(&ugeth->rx_recycle, skb);
 			}
 
-- 
1.7.0.4

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