Re: [PATCH net-next v2 2/5] net: openvswitch: set max limitation to meters

[Pravin Shelar <pravin.ovn@gmail.com>]

On Sat, Apr 18, 2020 at 10:25 AM <xiangxia.m.yue@gmail.com> wrote:
>
> From: Tonghao Zhang <xiangxia.m.yue@gmail.com>
>
> Don't allow user to create meter unlimitedly,
> which may cause to consume a large amount of kernel memory.
> The 200,000 meters may be fine in general case.
>
> Cc: Pravin B Shelar <pshelar@ovn.org>
> Cc: Andy Zhou <azhou@ovn.org>
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
> ---
>  net/openvswitch/meter.c | 21 +++++++++++++++------
>  net/openvswitch/meter.h |  1 +
>  2 files changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/net/openvswitch/meter.c b/net/openvswitch/meter.c
> index 494a0014ecd8..1b6776f9c109 100644
> --- a/net/openvswitch/meter.c
> +++ b/net/openvswitch/meter.c
> @@ -137,6 +137,7 @@ static int attach_meter(struct dp_meter_table *tbl, struct dp_meter *meter)
>  {
>         struct dp_meter_instance *ti = rcu_dereference_ovsl(tbl->ti);
>         u32 hash = meter_hash(ti, meter->id);
> +       int err;
>
>         /*
>          * In generally, slot selected should be empty, because
> @@ -148,16 +149,24 @@ static int attach_meter(struct dp_meter_table *tbl, struct dp_meter *meter)
>         dp_meter_instance_insert(ti, meter);
>
>         /* That function is thread-safe. */
> -       if (++tbl->count >= ti->n_meters)
> -               if (dp_meter_instance_realloc(tbl, ti->n_meters * 2))
> -                       goto expand_err;
> +       tbl->count++;
> +       if (tbl->count > DP_METER_NUM_MAX) {
> +               err = -EFBIG;
> +               goto attach_err;
> +       }
> +
> +       if (tbl->count >= ti->n_meters &&
> +           dp_meter_instance_realloc(tbl, ti->n_meters * 2)) {
> +               err = -ENOMEM;
> +               goto attach_err;
> +       }
>
>         return 0;
>
> -expand_err:
> +attach_err:
>         dp_meter_instance_remove(ti, meter);
>         tbl->count--;
> -       return -ENOMEM;
> +       return err;
>  }
>
>  static void detach_meter(struct dp_meter_table *tbl, struct dp_meter *meter)
> @@ -264,7 +273,7 @@ static int ovs_meter_cmd_features(struct sk_buff *skb, struct genl_info *info)
>         if (IS_ERR(reply))
>                 return PTR_ERR(reply);
>
> -       if (nla_put_u32(reply, OVS_METER_ATTR_MAX_METERS, U32_MAX) ||
> +       if (nla_put_u32(reply, OVS_METER_ATTR_MAX_METERS, DP_METER_NUM_MAX) ||
>             nla_put_u32(reply, OVS_METER_ATTR_MAX_BANDS, DP_MAX_BANDS))
>                 goto nla_put_failure;
>
> diff --git a/net/openvswitch/meter.h b/net/openvswitch/meter.h
> index d91940383bbe..cdfc6b9dbd42 100644
> --- a/net/openvswitch/meter.h
> +++ b/net/openvswitch/meter.h
> @@ -19,6 +19,7 @@ struct datapath;
>
>  #define DP_MAX_BANDS           1
>  #define DP_METER_ARRAY_SIZE_MIN        (1ULL << 10)
> +#define DP_METER_NUM_MAX       (200000ULL)
>
Lets make it configurable and default could 200k to allow
customization on different memory configurations.


>  struct dp_meter_band {
>         u32 type;
> --
> 2.23.0
>