From 2f09707d0c972120bf794cfe0f0c67e2c2ddb252 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
Date: Mon, 5 Sep 2022 21:21:36 +0200
Subject: [PATCH] sch_sfb: Also store skb len before calling child enqueue
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Git-commit: 2f09707d0c972120bf794cfe0f0c67e2c2ddb252
Patch-mainline: v6.0-rc5
References: CVE-2022-3586 bsc#1204439

Cong Wang noticed that the previous fix for sch_sfb accessing the queued
skb after enqueueing it to a child qdisc was incomplete: the SFB enqueue
function was also calling qdisc_qstats_backlog_inc() after enqueue, which
reads the pkt len from the skb cb field. Fix this by also storing the skb
len, and using the stored value to increment the backlog after enqueueing.

Fixes: 9efd23297cca ("sch_sfb: Don't assume the skb is still around after enqueueing to child")
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Acked-by: Cong Wang <cong.wang@bytedance.com>
Link: https://lore.kernel.org/r/20220905192137.965549-1-toke@toke.dk
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 net/sched/sch_sfb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sched/sch_sfb.c b/net/sched/sch_sfb.c
index 0d761f454ae8..2829455211f8 100644
--- a/net/sched/sch_sfb.c
+++ b/net/sched/sch_sfb.c
@@ -281,6 +281,7 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 {
 
 	struct sfb_sched_data *q = qdisc_priv(sch);
+	unsigned int len = qdisc_pkt_len(skb);
 	struct Qdisc *child = q->qdisc;
 	struct tcf_proto *fl;
 	struct sfb_skb_cb cb;
@@ -403,7 +404,7 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	memcpy(&cb, sfb_skb_cb(skb), sizeof(cb));
 	ret = qdisc_enqueue(skb, child, to_free);
 	if (likely(ret == NET_XMIT_SUCCESS)) {
-		qdisc_qstats_backlog_inc(sch, skb);
+		sch->qstats.backlog += len;
 		sch->q.qlen++;
 		increment_qlen(&cb, q);
 	} else if (net_xmit_drop_count(ret)) {
-- 
2.35.3