[PATCH v2] net/sched: mqprio: Add length check for TCA_MQPRIO_{MAX/MIN}_RATE64

[Lin Ma]

The nla_for_each_nested parsing in function mqprio_parse_nlattr() does
not check the length of the nested attribute. This can lead to an
out-of-attribute read and allow a malformed nlattr (e.g., length 0) to
be viewed as 8 byte integer and passed to priv->max_rate/min_rate.

This patch adds the check based on nla_len() when check the nla_type(),
which ensures that the length of these two attribute must equals
sizeof(u64).

Fixes: 4e8b86c06269 ("mqprio: Introduce new hardware offload mode and shaper in mqprio")
Signed-off-by: Lin Ma <linma@xxxxxxxxxx>
---
V1 -> V2: do check with != rather than < as suggested
          seperate the check and give clearer error message

 net/sched/sch_mqprio.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/net/sched/sch_mqprio.c b/net/sched/sch_mqprio.c
index ab69ff7577fc..f1d141a6d0aa 100644
--- a/net/sched/sch_mqprio.c
+++ b/net/sched/sch_mqprio.c
@@ -290,6 +290,13 @@ static int mqprio_parse_nlattr(struct Qdisc *sch, struct tc_mqprio_qopt *qopt,
 						    "Attribute type expected to be TCA_MQPRIO_MIN_RATE64");
 				return -EINVAL;
 			}
+
+			if (nla_len(attr) != sizeof(u64)) {
+				NL_SET_ERR_MSG_ATTR(extack, attr,
+						    "Attribute TCA_MQPRIO_MIN_RATE64 expected to have 8 bytes length");
+				return -EINVAL;
+			}
+
 			if (i >= qopt->num_tc)
 				break;
 			priv->min_rate[i] = nla_get_u64(attr);
@@ -312,6 +319,13 @@ static int mqprio_parse_nlattr(struct Qdisc *sch, struct tc_mqprio_qopt *qopt,
 						    "Attribute type expected to be TCA_MQPRIO_MAX_RATE64");
 				return -EINVAL;
 			}
+
+			if (nla_len(attr) != sizeof(u64)) {
+				NL_SET_ERR_MSG_ATTR(extack, attr,
+						    "Attribute TCA_MQPRIO_MAX_RATE64 expected to have 8 bytes length");
+				return -EINVAL;
+			}
+
 			if (i >= qopt->num_tc)
 				break;
 			priv->max_rate[i] = nla_get_u64(attr);
-- 
2.17.1