netdev - [PATCH v2 1/1] net/sched: taprio: Check if socket flags are valid

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Date:   Fri,  8 Apr 2022 11:47:45 +0200
From:   Benedikt Spranger <b.spranger@...utronix.de>
To:     netdev@...r.kernel.org
Cc:     Kurt Kanzenbach <kurt@...utronix.de>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Vedang Patel <vedang.patel@...el.com>
Subject: [PATCH v2 1/1] net/sched: taprio: Check if socket flags are valid

A user may set the SO_TXTIME socket option to ensure a packet is send
at a given time. The taprio scheduler has to confirm, that it is allowed
to send a packet at that given time, by a check against the packet time
schedule. The scheduler drop the packet, if the gates are closed at the
given send time.

The check, if SO_TXTIME is set, may fail since sk_flags are part of an
union and the union is used otherwise. This happen, if a socket is not
a full socket, like a request socket for example.

Add a check to verify, if the union is used for sk_flags.

Fixes: 4cfd5779bd6e ("taprio: Add support for txtime-assist mode")
Signed-off-by: Benedikt Spranger <b.spranger@...utronix.de>
Reviewed-by: Kurt Kanzenbach <kurt@...utronix.de>
Acked-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
---
 net/sched/sch_taprio.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 1ce6416b4810..a871b3ef4bca 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -419,7 +419,8 @@ static int taprio_enqueue_one(struct sk_buff *skb, struct Qdisc *sch,
 {
 	struct taprio_sched *q = qdisc_priv(sch);
 
-	if (skb->sk && sock_flag(skb->sk, SOCK_TXTIME)) {
+	/* sk_flags are only safe to use on full sockets. */
+	if (skb->sk && sk_fullsock(skb->sk) && sock_flag(skb->sk, SOCK_TXTIME)) {
 		if (!is_valid_interval(skb, sch))
 			return qdisc_drop(skb, sch, to_free);
 	} else if (TXTIME_ASSIST_IS_ENABLED(q->flags)) {
-- 
2.20.1