4.15-stable review patch.  If anyone has any objections, please let me know.

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

From: Paolo Abeni <pab...@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 <pab...@redhat.com>
Acked-by: Cong Wang <xiyou.wangc...@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@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
@@ -544,6 +544,7 @@ static void u32_remove_hw_knode(struct t
 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 tcf_block *block = tp->chain->block;
        struct tc_cls_u32_offload cls_u32 = {};
        bool skip_sw = tc_skip_sw(flags);
@@ -563,7 +564,7 @@ static int u32_replace_hw_knode(struct t
        cls_u32.knode.sel = &n->sel;
        cls_u32.knode.exts = &n->exts;
        if (n->ht_down)
-               cls_u32.knode.link_handle = n->ht_down->handle;
+               cls_u32.knode.link_handle = ht->handle;
 
        err = tc_setup_cb_call(block, NULL, TC_SETUP_CLSU32, &cls_u32, skip_sw);
        if (err < 0) {
@@ -840,8 +841,9 @@ 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);
@@ -859,11 +861,11 @@ 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


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