linux-kernel - [PATCH 1/3] Fix use of skb after netif

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Message-ID: <Pine.LNX.4.64.0712092101160.11165@ask.diku.dk>
Date:	Sun, 9 Dec 2007 21:02:31 +0100 (CET)
From:	Julia Lawall <julia@...u.dk>
To:	jdike@...aya.com, wangchen@...fujitsu.com,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH 1/3] Fix use of skb after netif_rx

From: Julia Lawall <julia@...u.dk>

Recently, Wang Chen submitted a patch
(d30f53aeb31d453a5230f526bea592af07944564) to move a call to netif_rx(skb)
after a subsequent reference to skb, because netif_rx may call kfree_skb on
its argument.  The same problem occurs in some other drivers as well.

This was found using the following semantic match.
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
expression skb, e,e1;
@@

(
 netif_rx(skb);
|
 netif_rx_ni(skb);
)
  ... when != skb = e
(
  skb = e1
|
* skb
)
// </smpl>

Signed-off-by: Julia Lawall <julia@...u.dk>
---

diff a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c
--- a/arch/um/drivers/net_kern.c	2007-11-15 15:09:36.000000000 +0100
+++ b/arch/um/drivers/net_kern.c	2007-12-05 19:01:14.000000000 +0100
@@ -98,10 +98,10 @@ static int uml_net_rx(struct net_device 
 	if (pkt_len > 0) {
 		skb_trim(skb, pkt_len);
 		skb->protocol = (*lp->protocol)(skb);
-		netif_rx(skb);
 
 		lp->stats.rx_bytes += skb->len;
 		lp->stats.rx_packets++;
+		netif_rx(skb);
 		return pkt_len;
 	}
 
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