netdev - [Xen-devel] [PATCH 1/1] xen/netback: only non-freed SKB is queued into tx

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Date:	Wed, 27 Jun 2012 18:46:58 +0800
From:	annie.li@...cle.com
To:	xen-devel@...ts.xensource.com, netdev@...r.kernel.org,
	davem@...emloft.net, Ian.Campbell@...rix.com,
	konrad.wilk@...cle.com
Cc:	kurt.hackel@...cle.com, annie.li@...cle.com,
	Annie Li <Annie.li@...cle.com>
Subject: [Xen-devel] [PATCH 1/1] xen/netback: only non-freed SKB is queued into tx_queue

From: Annie Li <Annie.li@...cle.com>

After SKB is queued into tx_queue, it will be freed if request_gop is NULL.
However, no dequeue action is called in this situation, it is likely that
tx_queue constains freed SKB. This patch should fix this issue, and it is
based on 3.5.0-rc4+.

This issue is found through code inspection, no bug is seen with it currently.
I run netperf test for several hours, and no network regression was found.

Signed-off-by: Annie Li <annie.li@...cle.com>
---
 drivers/net/xen-netback/netback.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index f4a6fca..682633b 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1363,8 +1363,6 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 					     INVALID_PENDING_IDX);
 		}
 
-		__skb_queue_tail(&netbk->tx_queue, skb);
-
 		netbk->pending_cons++;
 
 		request_gop = xen_netbk_get_requests(netbk, vif,
@@ -1376,6 +1374,8 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 		}
 		gop = request_gop;
 
+		__skb_queue_tail(&netbk->tx_queue, skb);
+
 		vif->tx.req_cons = idx;
 		xen_netbk_check_rx_xenvif(vif);
 
-- 
1.7.6.5

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