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    Subject[PATCH 4.9 27/92] cls_u32: add missing RCU annotation.
    Date
    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

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