[PATCH 4.14 040/185] net_sched: add max len check for TCA_KIND

[Greg Kroah-Hartman]

From: Cong Wang <xiyou.wangcong@xxxxxxxxx>

[ Upstream commit 62794fc4fbf52f2209dc094ea255eaef760e7d01 ]

The TCA_KIND attribute is of NLA_STRING which does not check
the NUL char. KMSAN reported an uninit-value of TCA_KIND which
is likely caused by the lack of NUL.

Change it to NLA_NUL_STRING and add a max len too.

Fixes: 8b4c3cdd9dd8 ("net: sched: Add policy validation for tc attributes")
Reported-and-tested-by: syzbot+618aacd49e8c8b8486bd@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Reviewed-by: David Ahern <dsahern@xxxxxxxxx>
Acked-by: Jiri Pirko <jiri@xxxxxxxxxxxx>
Signed-off-by: Jakub Kicinski <jakub.kicinski@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/sched/sch_api.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1217,7 +1217,8 @@ check_loop_fn(struct Qdisc *q, unsigned
  */
 
 const struct nla_policy rtm_tca_policy[TCA_MAX + 1] = {
-	[TCA_KIND]		= { .type = NLA_STRING },
+	[TCA_KIND]		= { .type = NLA_NUL_STRING,
+				    .len = IFNAMSIZ - 1 },
 	[TCA_RATE]		= { .type = NLA_BINARY,
 				    .len = sizeof(struct tc_estimator) },
 	[TCA_STAB]		= { .type = NLA_NESTED },