[patch 04/40] pkt_sched: cls_u32: Fix locking in u32_change()

[Greg KH]

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

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

From: Jarek Poplawski <jarkao2@xxxxxxxxx>

[ Upstream commit: 6f57321422e0d359e83c978c2b03db77b967b7d5 ]

New nodes are inserted in u32_change() under rtnl_lock() with wmb(),
so without tcf_tree_lock() like in other classifiers (e.g. cls_fw).
This isn't enough without rmb() on the read side, but on the other
hand adding such barriers doesn't give any savings, so the lock is
added instead.

Reported-by: m0sia <m0sia@xxxxxxxxxxx>
Signed-off-by: Jarek Poplawski <jarkao2@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 net/sched/cls_u32.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -637,8 +637,9 @@ static int u32_change(struct tcf_proto *
 				break;
 
 		n->next = *ins;
-		wmb();
+		tcf_tree_lock(tp);
 		*ins = n;
+		tcf_tree_unlock(tp);
 
 		*arg = (unsigned long)n;
 		return 0;

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