[PATCH 5.15 077/155] net/sched: mqprio: add extack to mqprio_parse_nlattr()

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Vladimir Oltean <vladimir.oltean@xxxxxxx>

[ Upstream commit 57f21bf85400abadac0cb2a4db5de1d663f8863f ]

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>
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Stable-dep-of: 6c58c8816abb ("net/sched: mqprio: Add length check for TCA_MQPRIO_{MAX/MIN}_RATE64")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 a5df5604e0150..4ec222a5530d1 100644
--- a/net/sched/sch_mqprio.c
+++ b/net/sched/sch_mqprio.c
@@ -131,7 +131,8 @@ static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
 }
 
 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 mqprio_sched *priv = qdisc_priv(sch);
 	struct nlattr *tb[TCA_MQPRIO_MAX + 1];
@@ -143,8 +144,11 @@ static int mqprio_parse_nlattr(struct Qdisc *sch, struct tc_mqprio_qopt *qopt,
 	if (err < 0)
 		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;
@@ -157,13 +161,19 @@ 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);
@@ -173,13 +183,19 @@ 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);
@@ -224,7 +240,7 @@ 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;
 	}
-- 
2.39.2