pkt_sched: cls_u32: Fix locking in u32_delete()

[Jarek Poplawski <jarkao2@gmail.com>]

pkt_sched: cls_u32: Fix locking in u32_delete()

While looking for a possible reason of bugzilla [Bug 11571]
"u32_classify Kernel Panic" reported by m0sia@plotinka.ru I found that
tcf_tree_lock() is missing in u32_delete() during u32_destroy_hnode()
call. Other paths calling this function use this lock. It haven't been
acknowledged this fixes the bug, but I think this patch is needed here
anyway.

Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>

---

 net/sched/cls_u32.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 246f906..9912ad5 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -433,7 +433,9 @@ static int u32_delete(struct tcf_proto *tp, unsigned long arg)
 
 	if (ht->refcnt == 1) {
 		ht->refcnt--;
+		tcf_tree_lock(tp);
 		u32_destroy_hnode(tp, ht);
+		tcf_tree_unlock(tp);
 	} else {
 		return -EBUSY;
 	}