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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Paolo Abeni <pabeni@redhat.com>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.9 27/92] cls_u32: add missing RCU annotation.
Date:   Fri,  9 Feb 2018 14:38:56 +0100
Message-Id: <20180209133933.184130086@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Paolo Abeni <pabeni@redhat.com>


[ Upstream commit 058a6c033488494a6b1477b05fe8e1a16e344462 ]

In a couple of points of the control path, n->ht_down is currently
accessed without the required RCU annotation. The accesses are
safe, but sparse complaints. Since we already held the
rtnl lock, let use rtnl_dereference().

Fixes: a1b7c5fd7fe9 ("net: sched: add cls_u32 offload hooks for netdevs")
Fixes: de5df63228fc ("net: sched: cls_u32 changes to knode must appear atomic to readers")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sched/cls_u32.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -496,6 +496,7 @@ static void u32_clear_hw_hnode(struct tc
 static int u32_replace_hw_knode(struct tcf_proto *tp, struct tc_u_knode *n,
 				u32 flags)
 {
+	struct tc_u_hnode *ht = rtnl_dereference(n->ht_down);
 	struct net_device *dev = tp->q->dev_queue->dev;
 	struct tc_cls_u32_offload u32_offload = {0};
 	struct tc_to_netdev offload;
@@ -520,7 +521,7 @@ static int u32_replace_hw_knode(struct t
 	offload.cls_u32->knode.sel = &n->sel;
 	offload.cls_u32->knode.exts = &n->exts;
 	if (n->ht_down)
-		offload.cls_u32->knode.link_handle = n->ht_down->handle;
+		offload.cls_u32->knode.link_handle = ht->handle;
 
 	err = dev->netdev_ops->ndo_setup_tc(dev, tp->q->handle,
 					    tp->protocol, &offload);
@@ -788,8 +789,9 @@ static void u32_replace_knode(struct tcf
 static struct tc_u_knode *u32_init_knode(struct tcf_proto *tp,
 					 struct tc_u_knode *n)
 {
-	struct tc_u_knode *new;
+	struct tc_u_hnode *ht = rtnl_dereference(n->ht_down);
 	struct tc_u32_sel *s = &n->sel;
+	struct tc_u_knode *new;
 
 	new = kzalloc(sizeof(*n) + s->nkeys*sizeof(struct tc_u32_key),
 		      GFP_KERNEL);
@@ -807,11 +809,11 @@ static struct tc_u_knode *u32_init_knode
 	new->fshift = n->fshift;
 	new->res = n->res;
 	new->flags = n->flags;
-	RCU_INIT_POINTER(new->ht_down, n->ht_down);
+	RCU_INIT_POINTER(new->ht_down, ht);
 
 	/* bump reference count as long as we hold pointer to structure */
-	if (new->ht_down)
-		new->ht_down->refcnt++;
+	if (ht)
+		ht->refcnt++;
 
 #ifdef CONFIG_CLS_U32_PERF
 	/* Statistics may be incremented by readers during update