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

Greg KH
2009-01-23T06:17:45Z

[-- Attachment #1: pkt_sched-cls_u32-fix-locking-in-u32_change.patch --]
[-- Type: text/plain, Size: 1032 bytes --]

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

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

From: Jarek Poplawski <jarkao2@gmail.com>

[ 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@plotinka.ru>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
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;