Re: [PATCH v4 net-next 3/9] net/sched: mqprio: add extack to mqprio_parse_nlattr()

[Jamal Hadi Salim]

On Mon, Apr 3, 2023 at 6:35 AM Vladimir Oltean <vladimir.oltean@xxxxxxx> wrote:
>
> Netlink attribute parsing in mqprio is a minesweeper game, with many
> options having the possibility of being passed incorrectly and the user
> being none the wiser.
>
> Try to make errors less sour by giving user space some information
> regarding what went wrong.
>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
> Reviewed-by: Ferenc Fejes <fejes@xxxxxxxxxxx>
> Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxx>

Acked-by: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>

cheers,
jamal

> ---
> v1->v4: none
>
>  net/sched/sch_mqprio.c | 30 +++++++++++++++++++++++-------
>  1 file changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/net/sched/sch_mqprio.c b/net/sched/sch_mqprio.c
> index 94093971da5e..5a9261c38b95 100644
> --- a/net/sched/sch_mqprio.c
> +++ b/net/sched/sch_mqprio.c
> @@ -150,7 +150,8 @@ static const struct nla_policy mqprio_policy[TCA_MQPRIO_MAX + 1] = {
>   * TCA_OPTIONS, which are appended right after struct tc_mqprio_qopt.
>   */
>  static int mqprio_parse_nlattr(struct Qdisc *sch, struct tc_mqprio_qopt *qopt,
> -                              struct nlattr *opt)
> +                              struct nlattr *opt,
> +                              struct netlink_ext_ack *extack)
>  {
>         struct nlattr *nlattr_opt = nla_data(opt) + NLA_ALIGN(sizeof(*qopt));
>         int nlattr_opt_len = nla_len(opt) - NLA_ALIGN(sizeof(*qopt));
> @@ -167,8 +168,11 @@ static int mqprio_parse_nlattr(struct Qdisc *sch, struct tc_mqprio_qopt *qopt,
>                         return err;
>         }
>
> -       if (!qopt->hw)
> +       if (!qopt->hw) {
> +               NL_SET_ERR_MSG(extack,
> +                              "mqprio TCA_OPTIONS can only contain netlink attributes in hardware mode");
>                 return -EINVAL;
> +       }
>
>         if (tb[TCA_MQPRIO_MODE]) {
>                 priv->flags |= TC_MQPRIO_F_MODE;
> @@ -181,13 +185,19 @@ static int mqprio_parse_nlattr(struct Qdisc *sch, struct tc_mqprio_qopt *qopt,
>         }
>
>         if (tb[TCA_MQPRIO_MIN_RATE64]) {
> -               if (priv->shaper != TC_MQPRIO_SHAPER_BW_RATE)
> +               if (priv->shaper != TC_MQPRIO_SHAPER_BW_RATE) {
> +                       NL_SET_ERR_MSG_ATTR(extack, tb[TCA_MQPRIO_MIN_RATE64],
> +                                           "min_rate accepted only when shaper is in bw_rlimit mode");
>                         return -EINVAL;
> +               }
>                 i = 0;
>                 nla_for_each_nested(attr, tb[TCA_MQPRIO_MIN_RATE64],
>                                     rem) {
> -                       if (nla_type(attr) != TCA_MQPRIO_MIN_RATE64)
> +                       if (nla_type(attr) != TCA_MQPRIO_MIN_RATE64) {
> +                               NL_SET_ERR_MSG_ATTR(extack, attr,
> +                                                   "Attribute type expected to be TCA_MQPRIO_MIN_RATE64");
>                                 return -EINVAL;
> +                       }
>                         if (i >= qopt->num_tc)
>                                 break;
>                         priv->min_rate[i] = *(u64 *)nla_data(attr);
> @@ -197,13 +207,19 @@ static int mqprio_parse_nlattr(struct Qdisc *sch, struct tc_mqprio_qopt *qopt,
>         }
>
>         if (tb[TCA_MQPRIO_MAX_RATE64]) {
> -               if (priv->shaper != TC_MQPRIO_SHAPER_BW_RATE)
> +               if (priv->shaper != TC_MQPRIO_SHAPER_BW_RATE) {
> +                       NL_SET_ERR_MSG_ATTR(extack, tb[TCA_MQPRIO_MAX_RATE64],
> +                                           "max_rate accepted only when shaper is in bw_rlimit mode");
>                         return -EINVAL;
> +               }
>                 i = 0;
>                 nla_for_each_nested(attr, tb[TCA_MQPRIO_MAX_RATE64],
>                                     rem) {
> -                       if (nla_type(attr) != TCA_MQPRIO_MAX_RATE64)
> +                       if (nla_type(attr) != TCA_MQPRIO_MAX_RATE64) {
> +                               NL_SET_ERR_MSG_ATTR(extack, attr,
> +                                                   "Attribute type expected to be TCA_MQPRIO_MAX_RATE64");
>                                 return -EINVAL;
> +                       }
>                         if (i >= qopt->num_tc)
>                                 break;
>                         priv->max_rate[i] = *(u64 *)nla_data(attr);
> @@ -252,7 +268,7 @@ static int mqprio_init(struct Qdisc *sch, struct nlattr *opt,
>
>         len = nla_len(opt) - NLA_ALIGN(sizeof(*qopt));
>         if (len > 0) {
> -               err = mqprio_parse_nlattr(sch, qopt, opt);
> +               err = mqprio_parse_nlattr(sch, qopt, opt, extack);
>                 if (err)
>                         return err;
>         }
> --
> 2.34.1
>