Re: [ovs-dev] [PATCH 1/1] openvswitch: check return value of nla_nest_start

[Pravin Shelar]

On Sat, Apr 22, 2017 at 11:43 PM, Pan Bian <bianpan2016@xxxxxxx> wrote:
> Function nla_nest_start() will return a NULL pointer on error, and its
> return value should be validated before it is used. However, in function
> queue_userspace_packet(), its return value is ignored. This may result
> in NULL dereference when calling nla_nest_end(). This patch fixes the
> bug.
>
> Signed-off-by: Pan Bian <bianpan2016@xxxxxxx>
> ---
>  net/openvswitch/datapath.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
> index 9c62b63..34c0fbd 100644
> --- a/net/openvswitch/datapath.c
> +++ b/net/openvswitch/datapath.c
> @@ -489,7 +489,8 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
>                 err = ovs_nla_put_tunnel_info(user_skb,
>                                               upcall_info->egress_tun_info);
>                 BUG_ON(err);
> -               nla_nest_end(user_skb, nla);
> +               if (nla)
> +                       nla_nest_end(user_skb, nla);
There is enough memory allocated for the netlink message accounting
for all attributes beforehand. So it is not required to check retuned
'nla' after each attributes addition to the msg.


>         }
>
>         if (upcall_info->actions_len) {
> @@ -497,7 +498,7 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
>                 err = ovs_nla_put_actions(upcall_info->actions,
>                                           upcall_info->actions_len,
>                                           user_skb);
> -               if (!err)
> +               if (!err && nla)
>                         nla_nest_end(user_skb, nla);
>                 else
>                         nla_nest_cancel(user_skb, nla);
> --
> 1.9.1
>
>
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