netdev - Re: [PATCH net 2/2] openvswitch: check for null return for nla_nest

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Date:   Wed, 18 Jul 2018 23:49:37 -0700
From:   Pravin Shelar <pshelar@....org>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        ovs dev <dev@...nvswitch.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>
Subject: Re: [PATCH net 2/2] openvswitch: check for null return for
 nla_nest_start in datapath

On Wed, Jul 18, 2018 at 9:12 AM, Stephen Hemminger
<stephen@...workplumber.org> wrote:
> The call to nla_nest_start when forming packet messages can lead to a NULL
> return so it's possible for attr to become NULL and we can potentially
> get a NULL pointer dereference on attr.  Fix this by checking for
> a NULL return.
>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=200537
> Fixes: 8f0aad6f35f7 ("openvswitch: Extend packet attribute for egress tunnel info")
> Signed-off-by: Stephen Hemminger <stephen@...workplumber.org>
> ---
>  net/openvswitch/datapath.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
> index 0f5ce77460d4..93c3eb635827 100644
> --- a/net/openvswitch/datapath.c
> +++ b/net/openvswitch/datapath.c
> @@ -460,6 +460,10 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
>
>         if (upcall_info->egress_tun_info) {
>                 nla = nla_nest_start(user_skb, OVS_PACKET_ATTR_EGRESS_TUN_KEY);
> +               if (!nla) {
> +                       err = -EMSGSIZE;
> +                       goto out;
> +               }
>                 err = ovs_nla_put_tunnel_info(user_skb,
>                                               upcall_info->egress_tun_info);
>                 BUG_ON(err);
> @@ -468,6 +472,10 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
>
>         if (upcall_info->actions_len) {
>                 nla = nla_nest_start(user_skb, OVS_PACKET_ATTR_ACTIONS);
> +               if (!nla) {
> +                       err = -EMSGSIZE;
> +                       goto out;
> +               }
>                 err = ovs_nla_put_actions(upcall_info->actions,
>                                           upcall_info->actions_len,
>                                           user_skb);

Acked-by: Pravin B Shelar <pshelar@....org>

Thanks.